    # Example 9 -- Plot dTdrho-rho section

    `Initialize Parameters'
    {
        \FILE_DATA = "example9a.dat" # T vs rho
        \FILE_LOCN = "example9b.dat" # section distances
        #
        # Following values from ~/eubex/processing/to_rho_bins/do_rho_inter
        \RHO_MIN = "28.1"
        \RHO_MAX = "27.5"
        \RHO_INC = "-0.002"
        \NY = "301"
        set missing value -99.0
        \xmin = "350"
        \xmax = "0"
        \xinc = "-100"
        \ymin = "28.1"
        \ymax = "27.8"
        \yinc = "-0.1"
        \zmin = "-10"		# black
        \zmax = "0"			# white
    }
    `Initialize Axes'
    Set up axes.
    {
        set x name "km"
        set x size 10
        set x axis \xmin \xmax \xinc
        set y size 5
        set y name "$\sigma_T$"
        set y axis label horizontal
        set y axis \ymin \ymax \yinc
        set y format %.1lf
        draw axes none
    }
    `Initialize Files'
    {
        query \data "Data file?   " ("\FILE_DATA")
        query \locn "Station locn?" ("\FILE_LOCN")
    }
    `Read Data'
    {
        # Read x-locations
        system awk '{print $2}' < \locn > TMP
        system wc TMP | awk '{print $1}' > NUM
        open NUM
        read .gridx_number.
        close
        system rm NUM
        open TMP
        read grid x .gridx_number.
        close
        system rm TMP
        # Create y-locations
        set y grid \RHO_MIN \RHO_MAX \RHO_INC
        #
        # Read data
        open \data
        read grid data \NY<font color=#CDAD00> .gridx_number.
        close
    }
    Initialize Parameters
    Initialize Axes
    Initialize Files
    Read Data
    set image range \zmin \zmax
    set image colorscale hsb 0 1 1 \zmin   hsb .6 1 1 \zmax
    convert grid to image box \xmin  \ymin \xmax \ymax
    #
    # Draw the image, then draw the axes.  Note that the image has
    # extends beyond the axes frame, so we will turn clipping
    # on before drawing it, to make a clean picture.
    set clip postscript on
    draw image
    set clip postscript off
    draw axes

    #
    # All done.
    draw title "Example 9"
    if {"\dohisto" == "yes"}
        draw title "Histogram enhanced grayscales"
    end if