Chapters:
1: Introduction
2: Simple example
3: Invocation
4: Finer Control
5: X-Y Plots
6: Contour Plots
7: Image Plots
8: Examples
9: Gri Commands
10: Programming
11: Environment
12: Emacs Mode
13: History
14: Installation
15: Gri Bugs
16: Test Suite
17: Gri in Press
18: Acknowledgments
19: License
Indices:
Concepts
Commands
Variables

### 9.3.41: The ``set`' commands

Set various flags and parameters which Gri will use in later commands.

- Set Axes Style: Set type of axes
- Set Arrow Size: Set size for arrow heads
- Set Arrow Type: Set type of arrow heads
- Set Beep: Set error beeping on or off
- Set Bounding Box: Set PostScript bounding box
- Set Clip: Set clipping region
- Set Color: Set color of pen
- Set Colorname: Create a color name
- Set Contour Format: Set format for numbers on contours
- Set Contour Label For: Set existence of contour labels
- Set Contour Label Position: Set spacing of contour labels
- Set Contour Labels: Control various things about contour lables
- Set Dash: Set style of dashed lines
- Set Environment: (Developer cmd)
- Set Error Action: Set error behavior
- Set Flag: Set flag to control Gri (developer cmd)
- Set Font Color: Set color of pen used for text
- Set Font Encoding: Set font encoding vector
- Set Font Size: Set size of text
- Set Font To: Set font for text
- Set Graylevel: Set graylevel of pen
- Set Grid Missing: Set missing region of grid
- Set Ignore Initial Newline: Set to ignore initial blank line
- Set Ignore Error Eof: Set ability to tolerate EOF on files
- Set Image Colorscale: Set colorscale mapping for image
- Set Image Grayscale: Set grayscale mapping for image
- Set Image Missing Value Color: Set missing value color in image
- Set Image Range: Set range of data that image can hold
- Set Input Data Window: Set data window for reading columns
- Set Input Data Separator: Set separator between data items
- Set Line Cap: Set line end (cap) type
- Set Line Join: Set method for intersections of line segments
- Set Line Width: Set width of lines
- Set Missing Value: Set "missing" value
- Set Page Size: Set page size
- Set Page: Set page style
- Set Panel: Establish geometry for a panel of multipanel plot
- Set Panels: Prepare for multipanel plot
- Set Path To: Set search-path for data or command files
- Set Postscript Filename: Set name of PostScript file
- Set Symbol Size: Set size of symbols
- Set Tic Size: Set size of tics on axes
- Set Trace: Set printout of statements as executed
- Set Transparency: Set transparency of the pen
- Set U Scale: Set scale for u (i.e. x) component of arrows
- Set V Scale: Set scale for v (i.e. y) component of arrows
- Set X Axis: Set range of x axis
- Set X Format: Set format for numbers on x axis
- Set X Grid: Set x mesh of contour grid
- Set X Margin: Set margin to left of x axis
- Set X Name: Set name of x axis
- Set X Size: Set length of x axis
- Set X Type: Set type of x axis (log/linear)
- Set Y Axis: Set range of y axis
- Set Y Format: Set format for numbers on y axis
- Set Y Grid: Set y mesh of contour grid
- Set Y Margin: Set margin below y axis
- Set Y Name: Set name of y axis
- Set Y Size: Set length of y axis
- Set Y Type: Set type of y axis (log/linear)
- Set Z Missing: Set missing region of z column

#### 9.3.41.1: ``set axes style`'

    set axes style .style.     \
      | {offset [.dist_cm.]} \
      | rectangular|none|default

Tell Gri how you want the axes to look, when they are drawn later.

- ``set axes style 0`' Set axes to be rectangular, with an x-y axis frame labelled at the left and bottom and tic marks on all axes.

- ``set axes style 1`' As style ``0`', but only put tics on the lower and left axes.

- ``set axes style 2`' As style ``0`' but without labels or tics on any axis, i.e. just an axis frame.

- ``set axes style offset [.dist_cm.]`' Set axes so that the actual x and y axes will be drawn with a space separating them from the data area. The space, if not set by the ``.distance_cm.`' option, will be equal to the current tic size (see ``set tic size`'). This command can be used together with any other ``set axes style`' command. It applies to both the ``draw axes`' command and with any ``draw x|y axis`' command in which the axis location is not explicitly given.

- ``set axes style rectangular`' Set axes to be rectangular, with an x-y axes frame labelled at the left and bottom.

- ``set axes style none`' Tell gri not to bother drawing axes before drawing curves, etc.

- ``set axes style default`' Same as ``set axes style 0`', and with ``offset`' turned off.

#### 9.3.41.2: ``set arrow size`'

    `set arrow size .size.           \
      | {as .num. percent of length} \
      | default'

Set the arrowsize (which is stored in the builtin variable ``..arrowsize..`').

- ``set arrow size .size.`' Set the arrow size (ie, half-width of the arrowhead) to ``.size.`' centimetres.

- ``set arrow size as .num. percent of length`' Set the arrow size to be the indicated percentage of arrow length, as in "HWP" in the singles ads. (As a flag to this, ``..arrowsize..`' is set to the negative of the fractional size measured in percent.)

- ``set arrow size default`' Set the arrow size to the default of 0.2 cm.

#### 9.3.41.3: ``set arrow type`'

    set arrow type .which.

Set type of arrow, according to the value of ``.which.`', rounded to the nearest integer. A rounded ``.which.`' value of 0 yields the default arrows, drawn with three line strokes. Value 1 yields outlined arrows, sometimes used on definition sketches. Value 2 yields filled, swept-back arrow heads.

This command uses the ``line join'' parameters that are presently active (see Set Line Join). So, by default, the arrow ends are rounded (because the default line-join parameter is 1). To get pointy ends, first set the line join parameter to 0.

#### 9.3.41.4: ``set beep`'

    `set beep on|off'

The command ``set beep on`' makes gri beep on errors and ``query`'. ``set beep off`' (the default) turns this beeping off.

#### 9.3.41.5: ``set bounding box`'

    `set bounding box .xleft. .ybottom. .xright. .ytop. [pt|cm]'

Set the PostScript bounding box for the graph to the indicated values. The bounding box is used by some programs to determine the region of the page on which marks have been made. For example, LaTeX uses the bounding box to decide how to position figures in documents.

Normally, the bounding box is computed automatically unless the ``-no_bounding_box`' commandline option has been specified; (see Invoking Gri). But if ``set bounding box`' is done, the automatically computed value is ignored and the given box is used instead. Use this if Gri makes mistakes in its automatic selection of bounding box.

The coordinates of the bounding box may be specified in (1) user coordinates, as defined at the moment the command is executed, or (2) in points on the page, measured from an origin at the lower-left (72 point per inch), or (3) in centimeters on the page. Which coordinate system is used depends on the last keyword -- use ``pt`' for points, ``cm`' for centimeters, and nothing at all for user-units.

The most common use is in points, since that is how many other application packages, e.g. LaTeX and dvips, specify the bounding box.

If the box is specified in the user units, the user units in effect at the moment of executing the ``set bounding box`' command are used. This must be born in mind if the coordinate system is changing during the execution of the program, e.g. if margins are changing or the x and y axes are changing. For this reason it often makes sense to put this command at the end of the commandfile.

#### 9.3.41.6: ``set clip`'

    `set clip [postscript] \
      {on [.xleft. .xright. .ybottom. .ytop.]} \
      {to curve} \
      | off'

Control clipping of following drawing commands. Note that the commands have two styles, one of which includes the keyword ``postscript`'. PostScript clipping does a cleaner job, but it results in larger file sizes. Important if you are using ``postscript`' clipping, then you be sure to turn it off using ``set clip postscript off`', instead of ``set clip off`'; otherwise Gri will get mixed up.

- ``set clip on`' Don't plot data outside axes.

- ``set clip postscript on`' As above, but Postscript clipping.

- ``set clip on .xleft. .xright. .ybottom. .ytop.`' Don't plot data outside indicated box.

- ``set clip postscript on .xleft. .xright. .ybottom. .ytop.`' As above, but Postscript clipping.

- ``set clip off`' Plot all data, whether inside the axes or not.

- ``set clip postscript off`' As above, but Postscript clipping.

- ``set clip to curve`' set clip to the curve, as would be drawn by a ``draw curve filled`' command, i.e. to the polygon constructed by running along the xy points, in order, followed by a final segment from the last point back to the first point. This is a "postscript" clip, as explained in the next item.

- ``set clip postscript to curve`' As above, but Postscript clipping.

      draw axes
      set clip postscript on 10 20 0 1
      draw curve
      set clip postscript off

- ``set clip postscript off`' Turn PostScript clipping off. See also ``set input data window`'.

#### 9.3.41.7: ``set color`'

    `set color \name               | \
        {rgb .red. .green. .blue.} | \
    {hsb .hue. .saturation. .brightness.}'

Set the color of the ``pen'' used for drawing lines and text. Normally lines and text are drawn in the same color, but the text color can be specified independently if desired (see Set Font Color). This might be useful to get contour lines of one color and labels of another. The spelling ``colour`' is also accepted.

In the ``set color \name`' style, set the drawing color to the indicated name, either from the builtin list (``white`', ``LightGray`', ``darkslategray`', ``black`', ``red`', ``brown`', ``tan`', ``orange`', ``yellow`', ``green`', ``ForestGreen`', ``cyan`', ``blue`', ``skyblue`', ``magenta`'), or from a list created by ``read colornames`'. In the latter case, if the colorname has more than one word in it, use quotes, e.g. ``set color "ghost white"`'. In the ``set color rgb ...`' style, set the individual color components as indicated. The numbers ``.red.`', ``.green.`' and ``.blue.`' range from 0 (for no contribution of that color component to the final color) to 1 (for maximal contribution). Values less than 0 are clipped to 0; values greater than 1 are clipped to 1. EXAMPLES:

    set color rgb 0   0   0 # black
    set color rgb 1   1   1 # white
    set color rgb 1   0   0 # bright red
    set color rgb 0.5 0   0 # dark red (only 50 percent)
    set color rgb 0   1   0 # pure green
    set color rgb 1   1   0 # yellow: red + green

In the ``set color hsb ...`' style, set the individual color components as indicated. The numbers ``.hue.`', ``.saturation.`' and ``.brightness.`' range from 0 to 1. The color, represented by .hue., ranges from 0 for pure red, through 1/3 for pure green, and 2/3 for pure blue, and back to 1 again for pure red. The purity of the color, represented by .saturation., ranges from 0 (none of the hue is visible) to 1 (the maximal amount is present). The brightness of the color, represented by ``.brightness.`', ranges from 0 (black) to 1 (maximal brigntness). Values less than 0 are clipped to 0; values greater than 1 are clipped to 1. EXAMPLES:

    set color hsb 0    1   1 # pure, bright red
    set color hsb 0    1 0.5 # half black, half red
    set color hsb .333 1   1 # pure, bright green

#### 9.3.41.8: ``set colorname`'

    `set colorname \name {rgb .red. .green. .blue.} \
                       | {hsb .hue. .saturation. .brightness.}'

Create a colorname with the indicated color. The color components range from 0 to 1, and will be clipped to these values if they are outside this range. EXAMPLE (borrowing a color from ``/usr/lib/X11/rgb.txt`'):

    set colorname peachpuff rgb 1 {rpn 218 255 / }  {rpn 185 255 / }
    draw box filled 2 2 3 3 cm

This command is akin to ``read colornames`' (see Read Colornames), except that the latter uses an X11 database, so the color constituents range from 0 to 255, whereas for ``set colorname`' they range from 0 to 1.

#### 9.3.41.9: ``set contour format`'

    `set contour format \style|default'

Normally, Gri draws the numeric labels of contours using a format code called ``%g`' in the "C" language. You may specify any other "long" format using this command. For example, ``set contour format %.1f`' tells Gri to use one decimal place in the numbers, and also to prefer the "float" notation to the exponential notation. ``set contour format default`' resets to the default ``%f`' format. You may use quotes around the format if you need to, to make the item be a single word (e.g. ``set contour format "%.1f m/s"`').

#### 9.3.41.10: ``set contour label for`'

    `set contour label for lines exceeding .x. cm'

Make it so contour lines shorter than ``.x.`' centimeters will not be labelled.

#### 9.3.41.11: ``set contour label position`'

    `set contour label position \
      {.start_cm. .between_cm.} \
      | centered \
      | default'

By default, contour labels are drawn at the location 1 cm into the contour curve, measured from the startpoint of the contour (e.g., for contours crossing the axes frames, the label will be 1 cm from the frame), and then at a uniform distance along the contour. By default, this uniform distance is the average dimension of the plotting area inside the axes. If ``.start_cm.`' and ``.between_cm.`' are specified, the first label is drawn at a distance ``.start_cm.`' from the start of the contour, and thereafter at a separation of ``.between_cm.`'.

If the ``centered`' option is used, then the contour labels are centered along the length of the line.

#### 9.3.41.12: ``set contour labels`'

    set contour labels rotated \
      | horizontal \
      | whiteunder \
      | nowhiteunder

The first two options control whether contour labels are rotated to line up with the contour lines, or whether they are horizontal (the default).

The second two options control whether the region under contour labels is whited out before drawing the label. The default is ``whiteunder`', which has the visual effect of the label having been drawn on a piece of paper and then pasted on. This can look jarring when the material under the contour is an image. When ``nowhiteunder`' is specified, the contour line is broken to make space for the text, but no whiting out is done.

#### 9.3.41.13: ``set dash`'

    `set dash [.n.|{.dash_cm. .blank_cm. ...}|off]'

Control dash-style for following ``draw curve`' and ``draw line`' commands.

- ``set dash`' Set to dashed line (0.4cm dashes, 0.1cm blanks).

- ``set dash .n.`' Set to indicated pre-defined dashed line, according to table:

      .n. dash/cm blank/cm
       0        -        -   ... (Solid line)
       1      0.2      0.1
       2      0.4      0.1
       3      0.6      0.1
       4      0.8      0.1
       5      1.0      0.1
      10      w        w
      11      w        2w
      12      w        3w
      13      w        4w
      14      w        5w
      15      w        6w

  Where ``w`' is written, it indicates the current linewidth. Thus, types 10 through 15 give square-dotted lines.

- ``set dash .dash_cm. .blank_cm. .dash_cm. .blank_cm. ...`' Set to indicated dashed line. The series of lengths ``.dash_cm.`' and ``.blank_cm.`' give the lengths of dash and blank portions (measured in centimeters). Any number of dash/blank lengths may be given. For example, ``set dash 0.5 0.1 0.1 0.1`' looks good.
- ``set dash off`' Turn dashing off, setting to a solid line.

#### 9.3.41.14: ``set environment`'

    `set environment'

Set environment (graylevel, axis length, etc) so that following plotting commands will make use of anything set by either a ``set`' command or by direct manipulation of builtin variables like ``..xsize..`', etc. NOTE: this should only be done by developers.

#### 9.3.41.15: ``set error`'

    `set error action to core dump'

Make Gri dump core when any error is found, to facilitate debugging.

#### 9.3.41.16: ``set flag`'

    `set flag \name [off]'

Set the indicated flag to YES. The name of the flag is contained in a single word, e.g. ``set flag dan_28sep_test`'. The action of the flags may change with time and is undocumented. This command is provided to enable selected users (e.g., the developer himself) to use test features of Gri before they are frozen into a fixed syntax and action. The keyword ``off`' turns the indicated flag off. NOTE: this should only be done by developers.

    FLAG         DATE     ACTION

    jinyu1       29sep94  'convert columns to grid'
                           outputs (x,y,z,z_predicted)

    emulate_gre   9jun97  'E' format on axes yields
                          scientific notation

    kelley1      17jun97  for kelley only - quit contour
                          trace if hit nonlegit

    kelley2      17jun97  for kelley only: print
                          info while contour tracing

#### 9.3.41.17: ``set font color`'

    set font color \name           | \
        {rgb .red. .green. .blue.} | \
    {hsb .hue. .saturation. .brightness.}

The syntax is the same as ``set color`', except that this applies to text only. By default, text is drawn in the same color as lines, so text color is changed as line color is changed (e.g. by using the ``set color`' or ``set graylevel`' commands)). However, once ``set font color`' is used in a Gri program, the font thereafter maintains a separate color from the lines.

#### 9.3.41.18: ``set font encoding`'

    set font encoding PostscriptStandard | isolatin1

Permits one to control the so-called ``font encoding'' used in text. The default font encoding is ISO-Latin-1, which is best for English and other European languages. To learn how to enter accents in a text editor, and for a brief overview of font encodings, (see Non-English Text).

If the so-called ``Postscript Standard'' font encoding is required, this command permits changing the encoding.

Note: few users will ever need this command. If you don't even know what ``font encoding'' is about, ignore this command!

#### 9.3.41.19: ``set font size`'

    `set font size {.size. [cm]}|default'

Set the size of the font for drawing of text.

- ``set font size .size.`' Set font size to ``.size.`' points. (A point is 1/72 of an inch, or 1/28 of a centimetre.)

- ``set font size .size. cm`' Set font size to ``.size.`' centimetres.

- ``set font size default`' Set font size to default = 12 pts.

If your figure is to be reproduced by a journal, you should check with them about the range of font size they need. This will, of course, depend on whether your figure is reduced or enlarged during reproduction. For example, American Geophysical Union (publishers of J. Geophysical Res.) recommends that one use fonts no smaller than 8 points. They also recommend that the range in fontsize in a given figure not exceed 2.

#### 9.3.41.20: ``set font to`'

    `set font to \fontname'

Set font to named style. Note that the backslash is not to be written, but here merely means that this word has several alternatives. For example, one might say ``set font to Courier`'. The allowed fontnames are: ``Courier`', a typewriter font (and the only monospaced font in Gri); ``Helvetica`' (the default), a sans-serif font commonly used in drafting scientific graphs; ``HelveticaBold`', a bold version of Helvetica; ``Times`' (also called ``TimesRoman`'), a font used in most newspapers; ``TimesBold`', a bold version of Times; ``Palatino`' (also called ``PalatinoRoman`'), similar to Times; ``Symbol`', included for completeness, is a mathematical font in which "a" becomes $\alpha$ of the math mode, etc. For reference on these fonts see any book on PostScript. The default font is ``Helvetica`'.

#### 9.3.41.21: ``set graylevel`'

    `set graylevel .brightness.|white|black'

Set graylevel for lines to indicated numerical value between 0=black and 1=white, or to the named color.

Note: if your diagram is to be reproduced by a journal, it is unlikely that the reproduction will be able to distinguish between any two graylevels which differ by less than 0.2. Also, graylevels less than 0.2 may appear as pure black, while those of 0.8 or more may appear as pure white. These guidelines are as specified by American Geophysical Union (publishers of J. Geophysical Res.), as of 1998.

#### 9.3.41.22: ``set grid missing`'

General format is

    `set grid missing \
      {above|below .intercept. .slope} \
      | {inside curve}'

The style

    `set grid missing above|below .intercept. .slope'

sets grid to missing value for all points above/below the line defined by

y = .intercept. + .slope. * x

The style

    `set grid missing inside curve'

sets the grid to the missing value throughout an area described by the curve last read in with ``read columns`'. This is useful for e.g. excluding land areas while contouring ocean properties. The curve may contain several "islands," each tracing (clockwise) a region inside of which the grid is to considered missing. If the first point in an island doesn't match the last, then an imaginary line is assumed which connects them. Multiple islands may be separated by missing-value codes.

See also ``Set Z Missing`'.

#### 9.3.41.23: ``set ignore initial newline`'

    `set ignore initial newline [off]'

Make Gri ignore a newline if it occurs as the first character of the next data file. This is used for files made by FORTRAN programs on VAX/VMS computers.

#### 9.3.41.24: ``set ignore error eof`'

    `set ignore error eof'

Stop Gri from considering that to encounter an end of file in future ``read`' commands consitutes an error; Gri will simply warn about future EOFs.

#### 9.3.41.25: ``set image colorscale`'

    set image colorscale hsb .h. .s. .b. .im_value. \
        hsb .h. .s. .b. .im_value. [increment .im_value.]
    set image colorscale rgb .r. .g. .b. .im_value. \
        rgb .r. .g. .b. .im_value. [increment .im_value.]
    set image colorscale \
      \name .im_value. \
      \name .im_value. \
      [increment .im_value.]

Set colorscale mapping for image, using HSB (hue, saturation, brightness) specification, RGB (red, green, blue) color specification, or named colors. The image range must previously have been set by ``set image range`', so that the ``.im_value.`' values will have meaning. Two pairs of (color, image-value) are given, and possibly an increment. Normally the colors are smoothly blended between the endpoints, but if an increment is supplied, the colors are quantized. The HSB method allows creation of spectral palettes, while the other two methods create simple blending between the two endpoints.

EG: To get a spectrum ranging between pure red (H=0) for image value of -10.0, and pure blue (H=2/3) for image value of 10.0, do this:

    set image colorscale hsb 0 1 1 -10 hsb .666 1 1 10

EG: To get a scale running from pure red (at image-value 10.0) into pure blue (at image-value 25.1), but with the colors blending intuitively in between (i.e., blending as paint might), use ``rgb`' color specification, as follows:

    set image colorscale rgb 1 0 0 10 rgb  0 0 1 25.1

EG: To get a quantized blend between the X11 colors ``skyblue`' at image value of 0 and ``tan`' at image value of 20, and with steps at image values incrementing by 5, do this:

    set image colorscale skyblue 0 tan 20 increment 5

Note that the traversal is through RGB space, so it is intuitive, not spectral. See ``set color`' for a list of X11 colors known to Gri.

See also ``read image colorscale`' (see Read Image Colorscale).

#### 9.3.41.26: ``set image grayscale`'

    `set image grayscale using histogram \
      [black .bl. white .wh.]'

    `set image grayscale \
      [black .bl. white .wh. [increment .inc.]]'

Set up a grayscale mapping for images. The image range must have previously have been set by ``set image range`'.

    `set image grayscale using histogram [black .bl. white .wh.]'

Create a grayscale mapping using linearized cumulative histogram enhancement. The image range must have previously have been set by ``set image range`'.

This creates maximal contrast in each range of graylevels, and is useful for tracing subtle features between different images (for example, it makes it easier to trace fronts between successive satellite images). The entire histogram is expanded, from the smallest value in the image to the largest.

With no options specified, the histogram is done from 0 in the image to 255 in the image. If the black/white options are specified, the histogram is done between these values.

    `set image grayscale \
      [black .bl. white .wh. [increment .inc.]]'

With no optional parameters, create a grayscale mapping for the current image, scaling it from black for the mininum value in the image to white for the maximum value. The image range must have previously have been set by ``set image range`'.

The optional parameters ``.wh.`' and ``.bl.`' specify the values to be drawn in white and black in the image, with smooth linear blending in between.

Normally the blending from white to black is smooth (linear), but if the additional optional parameter ``.inc.`' is specified, the blending is quantized, jumping to darker values at (``.wh.`' + ``.inc.`'), (``.wh.`' + 2* ``.inc.`'), etc. (The sign of ``.inc.`' will be altered, if necessary, to ensure that (``.wh.`' + ``.inc.`') is between ``.wh.`' and ``.inc.`'.) The colour switches to pure white at the value ``.wh.`', and remains pure white everywhere on the "white" side of this value. Similarly, the transition to pure black occurs at the value ``.bl.`'. In other words, neither pure white nor pure black is present inside the interval from ``.wh.`' to ``.bl.`'. Therefore, when using the ``draw image palette`' command, you might want to extend the range by one increment so as to get an example of both pure white and pure black.

    .w. = 0
    .b. = 1
    .i. = 0.2
    set image grayscale white .w. black .b. increment .i.
    draw image palette left \
      {rpn .w. .i. -} \
      right {rpn .b. .i. +} \
      increment .i.

#### 9.3.41.27: ``set image missing value color`'

    set image missing value color to white|black|\
        {graylevel .brightness.}|{rgb .r. .g. .b.}

Set the color of ``missing'' pixels (white by default). The image range must have previously have been set by ``set image range`'. Pixels with missing values can result from creating images from grids which have missing values; see the ``convert grid to image`' command. The ``.brightness.`' parameter in the ``graylevel`' style ranges from 0 for black to 1 for white. The ``rgb`' parameters allow setting to full color.

#### 9.3.41.28: ``set image range`'

    set image range .0value. .255value.

Specify maximum possible range of values that images can hold, in user units. Gri needs to know this because it stores images in a limited format capable of holding only 256 distinct values. Unlike some other programs, Gri encourages (forces) the user to specify things in terms of user-units, not image-units. This has the advantage of working regardless of the number of bits per pixel. Thus, for example, ``set image grayscale`', ``set image colorscale`', ``draw image grayscale`', etc, all use user units.

When an image is created by ``convert grid to image`', values outside the range spanned by ``.0value.`' and ``.255value.`' are clipped. (There is no need, however, for ``.0value.`' to be less than ``.255value.`'.) This clipping discards information, so make sure the range you give is larger than the range of data in the grid.

EXAMPLE: consider a satellite image in which an internal value of 0 is meant to correspond to 0 degrees Celsius, and an internal value of 255 corresponds to 25.5 degrees. (This is a common scale.) Then the Gri command ``set image range 0 25.5`' would establish the required range. If this range were combined with a linear grayscale mapping (see ``set image grayscale`'), the resultant granularity in the internal representation of the user values would be (25.5-0)/255 or 0.1 degrees Celsius; temperature variations from pixel to pixel which were less than 0.1 degrees would be lost.

All other image commands require that the range has been set. Thus, all these commands fail unless ``set image range`' has been done: ``draw image`', ``draw image palette`', ``read image`', ``convert grid to image`', ``set image grayscale`', and ``set image colorscale`'.

NOTE: If a range already exists when ``set image range`' is used, then the settings are altered. Thoughtless usage can therefore lead to confusing results. (The situation is like setting an axis scale, plotting a curve with no axes, then altering the scale and plotting the new axes. It is legal but not necessarily smart.)

#### 9.3.41.29: ``set input data window`'

    `set input data window x|y {.min. .max.}|off'

Create a data window for following ``read`' statements.

- ``set input data window x .min. .max.`' For future reading commands, ignore all data with x less than ``.min.`' or x greater than ``.max.`' The data not in the interval will not be read in at all. This will hold until ``set data window x off`' is done, in which case all data will be read in.

- ``set input data window x off`' Return to normal conditions, in which all data are read in.

- ``set input data window y .min. .max.`' Analgous to command for x.

- ``set input data window y off`' Analagous to command for x.

EXAMPLE: To set the input data window as the current x axis plus a border of 5 centimetres to left and right, do the following:

    set input data window x \
      {rpn ..xleft..  xusertocm 5 - xcmtouser} \
      {rpn ..xright.. xusertocm 5 + xcmtouser}

See also ``set clip`'

#### 9.3.41.30: ``set input data separator`'

    `set input data separator TAB|default'

Set the separator between data items. The ``default`' method is to assume that data items are separated by one or more spaces or tabs, and also to ignore any spaces or tabs at the start of a data line.

In the ``TAB`' method the data are assumed to be separated by a SINGLE tab character. (Multiple tabs will result in null values being assigned to items -- almost certainly not what you want!) Also, initial spaces and tabs on lines are NOT skipped.

Use the ``TAB`' method only after thinking carefully about the above, since the assignment of null values is problematic.

#### 9.3.41.31: ``set line cap`'

    `set line cap .type.'

Set the type of ends (caps) of lines. Use ``.type.`' of value 0 for square ends, cut off precisely at the end of line, or 1 for round ends which overhang half the line width, or 2 for square ends which overhang half the line width. The selected style is used for the ends of line segments, as well as at corners. In PostScript parlance, therefore, this command sets both the linecap and the linejoin parameters.

This command only applies to lines drawn with ``draw curve`', ``draw line`' and ``draw polygon`'. Axes are always drawn with a line cap of 0.

#### 9.3.41.32: ``set line join`'

    `set line join .type.'

Set the type of intersection of lines. Use ``.type.`' of value 0 for mitered joins (pointy ends that may extend beyond the data points), a value of 1 for rounded ends (the default), or a value of 2 for bevelled (squared-off) ends. See the ``setlinejoin`' command in any text on the PostScript language for more information.

This command only applies to lines drawn with ``draw curve`', ``draw line`' and ``draw polygon`'. Axes are always drawn with a line join of 0.

#### 9.3.41.33: ``set line width`'

    `set line width \
      [axis|symbol|all] \
      .width_pt. \
      | {rapidograph \name} \
      | default'

Set the width of lines used to draw curves (default), axes, symbols, or all of the above. The width may be set to a value specified in points (conversion: 72 pt = 1 inch), to a named rapidograph width, or to the default value. The initial default values are: 0.709pt (or rapidograph 3x0) for curves; 0.369pt (or rapidograph 6x0) for axes; 0.369pt (or rapidograph 6x0) for symbols. (To learn more about standard pen widths, see the ISO 9175-1 documents.)

If your figure is to be reproduced by a journal, you should check with them about the range of line thicknesses they recommend. This will, of course, depend on whether your figure is reduced or enlarged during reproduction. For example, American Geophysical Union (publishers of J. Geophysical Res.) recommends that one use line thicknesses no less than 0.5 points and no more than 4 points.

The rapidograph settings match the standard set of widths used in technical fountain pens. The table below gives width names along with the width in points and centimetres, as given in the specifications supplied with Rapidograph technical fountain pens. Names marked by the symbol ``*`' are in sequence increasing by the factor root(2). Texts on technical drawing often suggest using linewidths in the ratio of 2 or root(2). On many printers, the variation in width from root(2) increase is too subtle to see, so the factor-of-2 rule may be preferable. To get sizes in a sequence doubling in width, pick from the list (``6x0`', ``3x0`', ``1`', ``3.5`' ``7`'). To get a sequence increasing in width by root(2), pick from the list (``6x0`', ``4x0`', ``3x0`', ``0`', ``1`', ``2.5`', ``3.5`', ``6`', ``7`'). The eye can distinguish curves with linewidths differing by a factor of root(2) if the image is of high quality, but a factor of 2 is usually better. Similarly, for overhead projections and projected slides, one would do well to use linewidths differing by a factor of 4.

This is the list of ``rapidograph`' linewidths:

      Name      pt    cm
      ====    =====  =====
    *  6x0    0.369  0.013
    *  4x0    0.510  0.018
    *  3x0    0.709  0.025
        00    0.850  0.03
    *    0    0.992  0.035
    *    1    1.417  0.05
         2    1.701  0.06
    *    2.5  1.984  0.07
         3    2.268  0.08
    *    3.5  2.835  0.1
         4    3.402  0.12
    *    6    3.969  0.14
    *    7    5.669  0.2

#### 9.3.41.34: ``set missing value`'

    `set missing value .value.|none'

If a numerical value is given, set the missing-value code to that value, and also store this value in the builtin variable ``..missingvalue..`' and the builtin synonym ``\.missingvalue..`' also. After this command, Gri will ignore any data that are within 0.1 percent of this value. (This feature is commonly used in geophysical data.)

If ``none`' is given, turn off this feature.

The default is that the feature is turned off.

#### 9.3.41.35: ``set page size`'

    `set page size letter|legal|folio|tabloid|A0|A1|A2|A3|A4|A5'

Set the page dimension, as indicated below.

letter
  American "letter" size: 8.5 x 11 inches

legal
  American "legal" size: 8.5 x 14 inches

folio
  American "folio" size: 8.5 x 13 inches

tabloid
  American "tabloid" size: 11 x 17 inches

A5
  Metric size: 14.8 x 21.0 cm

A4
  Metric size: 21.0 x 29.7 cm

A3
  Metric size: 29.7 x 42.0 cm

A2
  Metric size: 42.0 x 59.4 cm

A1
  Metric size: 59.4 x 84.1 cm

A0
  Metric size: 84.1 x 118.9 cm

The effect is to possibly alter the PostScript "bounding box." If all the drawn material fits within the indicated page, then the bounding box is not altered. (In other words, Gri will still keep the bounding box tight on the drawn items.)

However, if any drawn item extends beyond the indicated size, it will be clipped to the boundary.

#### 9.3.41.36: ``set page`'

    `set page portrait \
      | landscape \
      | {factor .mag.} \
      | {translate .xcm. .ycm.}'

Control orientation or scaling of what is drawn on the paper.

- ``set page portrait`' Print graph normally (default).

- ``set page landscape`' Print graph sideways.

- ``set page factor .mag.`' Scale everything to be drawn on the paper by the indicated magnification factor. This must be called before any drawing commands.

- ``set page translate .xcm. .ycm.`' Translate everything to be drawn on the paper by the indicated x/y distances. This must be called before any drawing commands.

Note: The order of the factor/translate commands matters, so you may need to experiment. For example,

    set page translate 2 1
    set page factor 0.5

moves anything that would have been drawn at the lower-left corner of the paper onto the point 2cm from the left side and 1cm from the bottom side of the paper, and then applies the multiplication factor. Reversing the order gives quite different results. PostScript gurus should note that the following two commands are inserted into the PostScript file:

    56.900000 28.450000 translate
    0.500000 0.500000 scale

#### 9.3.41.37: ``set panel`'

    set panel .row. .col.

Establish the geometry for the panel in the indicated row and column; that is, select which defined panel to draw into. The bottom row has ``.row.`' = 1, and the leftmost column has ``.col.`' = 1. This must be used only after defining the panel layout using ``Panels .row. .col. .dx_cm. .dy_cm.`'.

#### 9.3.41.38: ``set panels`'

    set panels .rows. .cols. [.dx_cm. .dy_cm.]

Set up for multipanel plots, with spacing ``.dx_cm.`' between the columns and ``.dy_cm.`' between the rows. If the spacings are not supplied, 2cm is used. The panels fill the rectangle which would otherwise contain the single axis frame, as set by ``set x size`' and ``set x margin`', etc.

The global variables ``.panel_dx.`', ``.panel_dy.`', ``.panel_xmargin.`', ``.panel_ymargin.`', ``.panel_xsize.`', and ``.panel_ysize`' are created, to be used by later calls to ``set panel`'.

EXAMPLE

    # Draw 2 panels across, 3 up the page.

    # The Panel interiors will be in region cornered
    # by (2,2), (12,22) cm
    set x margin 2
    set y margin 2
    set x size 10
    set y size 20
    set panels 2 3

    # Create dummy scale
    set x axis 0 1
    set y axis 0 1

    # Draw blank axes
    et panel 1 1
    raw axes
    set panel 1 2
    draw axes
    set panel 1 3
    draw axes
    set panel 2 1
    draw axes
    set panel 2 2
    draw axes
    set panel 2 3
    draw axes

See also ``set panel .row. .col.`'

#### 9.3.41.39: ``set path`'

    set path to "\path"|default for data|commands

Set the directory path that ``open`' will search for data files, or that ``insert`' will search for command files. This search will not be done if the filename starts with a ``/`', ``~`', or ``.`' character.

The path is formatted in a colon-separated manner, following the normal Unix convention, and searching is from left to right. For example, the path ``".:/usr/lib/gri"`' tells Gri to search for the file first in the local directory (named ``.`'), and if it is not found there, to look next in the directory named ``/usr/lib/gri`'.

The indicated path is stored in either ``\.path_data.`' or ``\.path_commands.`', as appropriate. At startup time, each of these paths is set to ``"."`', the current directory, and this value is reset if the ``default`' keyword is provided to this command.

If you need to know where the file was eventually found, save the ``\.return_value.`' just after the ``open`' command was executed. For example, the following defines the synonym ``\uk`', which is the full pathname of the file containing some sort of data about Great Britain.

    set path to "/atlases/world:/atlases/northern_hemisphere" for data
    open britain.dat        # we don't know where file is ...
    \gb = "\.return_value." # ... until now!

    # Can later do command such as
    #    read from \gb
    # or
    #    rewind \gb
    # to work with this particular file, even if
    # there is another file open that also is
    # named "britain.dat".

#### 9.3.41.40: ``set postscript filename`'

    `set postscript filename "\name"'

Set name of PostScript file, over-riding the present name.

#### 9.3.41.41: ``set symbol size`'

    `set symbol size .diameter_cm.|default'

Control the diameter of symbols drawn by ``draw symbol`' command.

- ``set symbol size .diameter_cm.`' Make symbol size be ``.diameter_cm.`' centimeters in diameter.

- ``set symbol size default`' Set to default diameter of 0.1 cm.

#### 9.3.41.42: ``set tic size`'

    `set tic size .size.|default'

Control size of tics on axes.

- ``set tic size .size.`' Set tic size to ``.size.`' centimetres.

- ``set tic size default`' Set tic size to default of 0.2 cm.

- ``set tics in|out`' Make axis tics point inward or outward. The default is outward.

#### 9.3.41.43: ``set trace`'

    `set trace [on|off]'

Control printing of command lines as they are processed.

- ``set trace`' Make Gri print command lines as they are processed.

- ``set trace on`' Same as ``set trace`'.

- ``set trace off`' Prevent printing command lines (default).

#### 9.3.41.44: ``set transparency`'

    `set transparency .transparency.'

Set the transparency of drawn items, 0 for opaque and 1 for invisibly faint. This command is provisional, as of summer 2004, and this part of the documentation needs to be fleshed out so users can build intuition on transparency. For example, a quick quiz: what color do you think comes from drawing red on top of yellow, or on top of blue?

#### 9.3.41.45: ``set u scale`'

    `set u scale .cm_per_unit.|{as x}'

Set scale for x-component of arrows.

- ``set u scale .cm_per_unit.`' Set scale for ``u`' component of arrows.

- ``set u scale as x`' Set scale for u component of arrows to be the same as the x-scale. Equivalent to ``set u scale as {rpn ..xsize.. ..xright.. ..xleft.. - /}`'.

NOTE: this only works if the x-scale is LINEAR (see ``set x type`').

#### 9.3.41.46: ``set v scale`'

    `set v scale .cm_per_unit.|{as y}'

Set scale for y-component of arrows.

- ``set v scale .cm_per_unit.`' Set scale for ``v`' component of arrows.

- ``set v scale as y`' Set scale for v component of arrows to be the same as the y-scale. Equivalent to ``set v scale as {rpn ..ysize.. ..ytop.. ..ybottom.. - /}`'.

NOTE: this only works if the y-scale is LINEAR (see ``set y type`').

#### 9.3.41.47: ``set x axis`'

    `set x axis top'
    `set x axis bottom'
    `set x axis increasing'
    `set x axis decreasing'
    `set x axis unknown'
    `set x axis .left. .right. [.incBig. [.incSml.]]'
    `set x axis labels [add] .position_1. "label_1" [.position_2. "label_2" [...]]'
    `set x axis labels automatic'

Control various things about the x axis.

- ``set x axis top`' Make next x-axis to be drawn have labels above the axis.

- ``set x axis bottom`' Make next x-axis to be drawn have labels below the axis.

- ``set x axis increasing`' Make next x-axis to be drawn have numeric labels increasing to the right. This applies only if autoscaling is done; otherwise, the supplied values (``.left. .right. [.incBig. [.incSml.]]`') are used.

- ``set x axis decreasing`' Make next x-axis to be drawn have numeric labels decreasing to the right. This applies only if autoscaling is done; otherwise, the supplied values (``.left. .right. [.incBig. [.incSml.]]`') are used.

- ``set x axis unknown`' Make Gri forget any existing scale for the x axis, whether set by another ``set x axis`' command or automatically, during reading of data. This is essentially a synonym for ``delete x scale`'.

- ``set x axis .left. .right.`' Make x-axis range from ``.left.`' to ``.right.`'

- ``set x axis .left. .right. .incBig.`' Make x-axis range from ``.left.`' to ``.right.`', with labelled increments at ``.incBig.`' Note: In the case of log axes, and provided that ``set x type log`' has been called previously, the ``.incBig.`' parameter has a different meaning: it is the interval, in decades, between numbered labels; the default is 1.

- ``set x axis .left .right. .incBig. .incSml.`' Make x-axis range from ``.left.`' to ``.right.`', with labelled increments at ``.incBig.`', and small tics at ``.incSml.`' NOTE: if the axis is logarithmic, the value of ``.incSml.`' takes on a special meaning: if it is positive then small tics are put at values 2, 3, 4, etc. between the decades, but if ``.incSml.`' is negative then no such small tics are used.

- ``set x axis labels .position. "label" [.position. "label" [...]]`' Override the automatic labelling at axis tics, and instead put the indicated labels at the indicated x values. For example, a day-of-week axis can be created by the code:

      set x axis 0 7 1
      set x axis labels 0.5 "Mon" 1.5 "Tue" 2.5 "Wed" \
                        3.5 "Thu" 4.5 "Fri" 5.5 "Sat" \
                        6.5 "Sun"

  The command replaces any existing labels, unless the `add' keyword is present, in which case the new label information is appended to any existing information.

- ``set x axis labels automatic`' Return to automatically-generated axis labels, undoing the command of the previous item.

#### 9.3.41.48: ``set x format`'

    `set x format \format|default|off

Set format for numbers on x axis. The format is specified in the manner of the "C" programming language. The C formats (i.e., ``%f`', ``%e`' and ``%g`') are permitted. For example, ``set x format %.1f`' tells Gri to use 1 decimal place, and to prefer the "float" notation to the exponential notation. The form ``set x format off`' tells Gri not to write numbers on the axis. To get spaces in your format, enclose the format string in double-quotes, e.g., you might use ``set x format "%.0f$\circ$ W"`' for a map, or ``set x format "%f "`' to make the numbers appear to the left of their normal location.

The default format is ``%lg`'.

#### 9.3.41.49: ``set x grid`'

    `set x grid .left. .right. .inc.|{/.cols.}'

Create x-grid for contour or image. If a grid already exists, an error will be declared; the way to interpolate from an existing grid to a new one is with the ``interpolate x grid`' command.

- ``set x grid .left. .right. .inc.`' Create x-grid ranging from the value ``.left.`' at the left to ``.right.`' at the right, stepping by an increment of ``.inc.`'.

- ``set x grid .left. .right. /.cols.`' Create x-grid with ``.cols.`' points, ranging from the value ``.left.`' at the left to ``.right.`' at the right.

#### 9.3.41.50: ``set x margin`'

    `set x margin {[bigger|smaller] .size.}|default'

Control x margin, that is, the space between the left-hand side of the page and the left-hand side of the plotting area. (Note that axis labels are drawn inside the margin; the margin extends to the axis line, not to the labels.)

- ``set x margin .size.`' Set left margin to ``.size.`' cm. It is permissible to have negative margins, with the expected effect.

- ``set x margin bigger .size.`' Increases left margin by ``.size.`' cm.

- ``set x margin smaller .size.`' Decreases left margin by ``.size.`' cm.
- ``set x margin default`' Set left margin to default = 6 cm.

#### 9.3.41.51: ``set x name`'

    `set x name "\name"|default'

Set name of x-axis to the indicated string. An empty string (``set x name ""`') causes the x axis to be unlabelled. The ``default`' is ``"x"`'.

#### 9.3.41.52: ``set x size`'

    `set x size .width_cm.|default'

Set the width of the plotting area. This does not include axis labels, only the interior part of the plot.

- ``set x size .width_cm.`' Set width of x-axis in centimeters.

- ``set x size default`' Set width of x-axis to default = 10 cm.

#### 9.3.41.53: ``set x type`'

    set x type linear|log|{map E|W|N|S}

Control transformation function mapping user units to centimetres on the page.

- ``set x type linear`' Set to linear axis.

- ``set x type log`' Set to log axis. To avoid clashes in the linear to log transform, this command should precede the creation of an axis scale, either explicitly through the ``set x axis .left. .right. ...`' command or implicitly through the ``read columns`' command.

- ``set x type map E|W|N|S`' Set to be a map. This means that whole numbers on the axis will have a degree sign written after them (and then the letter ``E`', etc) and that numbers which are multiples of 1/60 will be written in degree-minute format, and that similarly numbers which are divisible by 1/3600 will be in degree-minute-second format. If none of these things apply, the axis labels will be written in decimal degrees. Note that this command overrides any format set by ``set x format`'.

  BUG: this only has an effect if the axis is not already of type ``log`'.

#### 9.3.41.54: ``set y axis`'

    `set y axis left'
    `set y axis right'
    `set y axis increasing'
    `set y axis decreasing'
    `set y axis .bottom. .top. [.incBig. [.incSml.]]'
    `set y axis labels [add] .position_1. "label_1" [.position_2. "label_2" [...]]'
    `set y axis labels automatic'

Control various things about the y axis.

- ``set y axis name horizontal`' Make y-axis name be horizontal.

- ``set y axis name vertical`' Make y-axis name be vertical (default).

- ``set y axis left`' Make next y-axis to be drawn have labels to the left of the axis.

- ``set y axis right`' Make next y-axis to be drawn have labels to the right of the axis.

- ``set y axis increasing`' Make next y-axis to be drawn have numeric labels increasing up the page. This applies only if autoscaling is done; otherwise, the supplied values (``.left. .right. [.incBig. [.incSml.]]`') are used.

- ``set y axis decreasing`' Make next y-axis to be drawn have numeric labels decreasing up the page. This applies only if autoscaling is done; otherwise, the supplied values (``.left. .right. [.incBig. [.incSml.]]`') are used.

- ``set y axis unknown`' Make Gri forget any existing scale for the y axis, whether set by another ``set y axis`' command or automatically, during reading of data. This is essentially a synonym for ``delete y scale`'.

- ``set y axis .bottom. .top.`' Make y-axis range from ``.bottom.`' to ``.top.`'

- ``set y axis .bottom. .top. .incBig.`' Make y-axis range from ``.bottom.`' to ``.top.`', with labelled increments at ``.incBig.`'

- ``set y axis .bottom. .top. .incBig. .incSml.`' Make y-axis range from ``.bottom.`' to ``.top.`', with labelled increments at ``.incBig.`', and small tics at ``.incSml.`' NOTE: if the axis is logarithmic, the value of ``.incSml.`' takes on a special meaning: if it is positive then small tics are put at values 2, 3, 4, etc. between the decades, but if ``.incSml.`' is negative then no such small tics are used.

- ``set y axis labels .position. "label" [.position. "label" [...]]`' Override the automatic labelling at axis tics, and instead put the indicated labels at the indicated y values. For example, a physical-condition axis can be created by the code:

      set y axis 0 1 0.5
      set y axis labels 0.25 "Weak" 0.75 "Strong"

  The command replaces any existing labels, unless the `add' keyword is present, in which case the new label information is appended to any existing information.

- ``set y axis labels automatic`' Return to automatically-generated axis labels, undoing the command of the previous item.

- ``set y axis name vertical`' Cause future y axes to be drawn with the name aligned vertically (the default).

- ``set y axis name horizontal`' Cause future y axes to be drawn with the name aligned horizontally.

#### 9.3.41.55: ``set y format`'

    `set y format \format|default|off'

Set format for numbers on y axis. The format is specified in the manner of the "C" programming language. The C formats (i.e., ``%f`', ``%e`' and ``%lg`') are permitted. For example, ``set y format %.1f`' tells Gri to use 1 decimal place, and to prefer the "float" notation to the exponential notation. The form ``set y format off`' tells Gri not to write numbers on the axis. To get spaces in your format, enclose the format string in double-quotes, e.g., you might use ``set y format "%.0f$\circ$ N"`' for a map, or ``set y format "%f"`' to make the numbers appear to the right of their normal location.

The default format is ``%lg`'.

#### 9.3.41.56: ``set y grid`'

    `set y grid .bottom. .top. .inc.|{/.rows.}'

Create y-grid for contour or image. If a grid already exists, an error will be declared; the way to interpolate from an existing grid to a new one is with the ``interpolate x grid`' command.

- ``set y grid .bottom. .top. .inc.`' Create y-grid ranging from the value ``.bottom.`' at the bottom to ``.top.`' at the top, stepping by an increment of ``.inc.`'.

- ``set y grid .bottom. .top. /.rows.`' Create y-grid with ``.rows.`' points, ranging from the value ``.bottom.`' at the bottom to ``.top.`' at the top.

#### 9.3.41.57: ``set y margin`'

    `set y margin {[bigger|smaller] .size.}|default'

Control y margin, that is, the space between the bottom side of the page and the bottom of the plotting area. (Note that axis labels are drawn inside the margin; the margin extends to the axis line, not to the labels.)

- ``set y margin .size.`' Set bottom margin to ``.size.`' centimeters. It is permissible to have negative margins, with the expected effect.

- ``set y margin bigger .size.`' Increases bottom margin by ``.size.`' centimeters.

- ``set y margin smaller .size.`' Decreases bottom margin by ``.size.`' centimeters.

- ``set y margin default`' Set bottom margin to default = 6 cm.

#### 9.3.41.58: ``set y name`'

    `set y name "\name"|default'

Set name of y-axis to the indicated string. An empty string (``set y name ""`') causes the x axis to be unlabelled. The ``default`' is ``"y"`'.

#### 9.3.41.59: ``set y size`'

    `set y size .height_cm.|default'

Set the width of the plotting area. This does not include axis labels, only the interior part of the plot.

- ``set y size .height_cm.`' Set height of y-axis in centimeters.

- ``set y size default`' Set width of y-axis to default = 10 cm.

#### 9.3.41.60: ``set y type`'

    set y type linear|log|{map N|S|E|W}

Control transformation function mapping user units to centimetres on the page.

- ``set y type linear`' Set to linear axis.

- ``set y type log`' Set to log axis. To avoid clashes in the linear to log transform, this command should precede the creation of an axis scale, either explicitly through the ``set y axis .left. .right. ...`' command or implicitly through the ``read columns`' command.

- ``set y type map N|S|E|W`' Set to be a map. This means that whole numbers on the axis will have a degree sign written after them (and then the letter ``N`', etc), and that numbers which are multiples of 1/60 will be written in degree-minute format, and that similarly numbers which are divisible by 1/3600 will be in degree-minute-second format. If none of these things apply, the axis labels will be written in decimal degrees. Note that this command overrides any format set by ``set y format`'.

  BUG: this only has an effect if the axis is not already of type ``log`'.

#### 9.3.41.61: ``set z missing`'

    set z missing above|below .intercept. .slope.

Set ``z`' column to be missing whenever the associated ``y`' and ``x`' columns are above/below the line defined by

y = .intercept. + .slope. * x