# The Plotter

Siag uses Gnuplot for plotting. Gnuplot is normally used interactively, that is, commands are entered on the command line. When used from Siag, however, Siag automatically produces data and command files which are then processed by Gnuplot, so that it is not necessary to learn any Gnuplot commands to produce graphs from Siag.

## Gnuplot Made Easy

To produce a graph from Siag, do the following:

1. Set the block on the data you want to plot
2. Click on the plotting icon

That's it. This will produce a graph using lines. If the top row in the block contains labels, these will automatically be used for tic marks on the x axis. If the leftmost column contains labels, these will automatically be used as titles for the graphs. Anything else is used as data with one dataset per line.

The Plot menu can be used to select other plot styles. These are available:

Lines
  Connects adjacent lines with points.
Points
  Displays a small symbol at each point.
Linespoints
  The linespoints style does both lines and points.
Impulses
  Displays a vertical line from the x axis to each point.
Dots
  Plots a tiny dot at each point.
Steps
  This style connects consecutive points with two line segments: the first from (x1,y1) to (x1,y2) and the second from (x1,y2) to (x2,y2).
Boxes
  The boxes style draws a box centered about the yaxis to the given y coordinate.

## Advanced Plotting

None of this is actually implemented yet. This only describes what I would eventually be able to do with Siag.

The "Advanced" plotting mode is only for users who are familiar with Gnuplot and the inner workings of Siag. It provides the possibility to plot anything that Gnuplot can plot, including 3D plots and plots where different datasets use different styles. The cost of this flexibility is that the plotting commands have to be entered as text.

The description below comes from the on-line help in Gnuplot. While the numerous parameters may seem intimidating, reasonable defaults are available for everything.

mode
  The two primary plotting modes are 2D and 3D.
title
  A title of each plot appears in the key
style
  Plots may be displayed in one of eight styles:
  lines
    Connects adjacent lines with points.
  points
    Displays a small symbol at each point.
  linespoints
    The linespoints style does both lines and points.
  impulses
    Displays a vertical line from the x axis (or from the grid base for 3D plots) to each point.
  dots
    Plots a tiny dot at each point.
  errorbars
    The errorbars style is only relevant for 2D plotting. It is like points, except that a vertical error bar is also drawn from (x,ylow) to (x,yhigh). A tic mark is placed at the ends of the error bar.
  steps
    This style connects consecutive points with two line segments: the first from (x1,y1) to (x1,y2) and the second from (x1,y2) to (x2,y2).
  boxes
    The boxes style is only relevant to 2D plotting. It draws a box centered about the yaxis to the given y coordinate.
  boxerrorbars
    This style is a combination is combination of the boxes and errorbars styles.
  labels
    The x- and y-axis have lables. The x label is centered along the x axis and the position of the y label depends on the terminal.
  terminal
    Selects the type of graphics device for which Gnuplot will produce output.
  output
    Directs the display to the specified file or device.
  logscale
    Log scaling may be set on the x, y, and z axes. Any combination of x, y and z axes may use log scaling. If the base is not set, 10 is assumed.
  tics
    Fine control of the axis tic marks is possible. See the documentation that comes with Gnuplot for more on this.
  grid
    If this is selected, a grid is drawn at the tic marks.
  time
    If selected, the time and date of the plot is placed at the top or bottom of the left margin. The exact location is device dependent.
  size
    Scales the displayed size of the plot.