    # Example 4 -- Simple contour graph

    #
    # Read x-grid; blank-line means stop reading.
    read grid x
    0
    .2
    1

    # Note that the x-grid was irregular.  The y-grid
    # in this example is regular, so we can just set
    # it to range from 10 to 20, incrementing by 2.5.
    set y grid 10 20 2.5
    # Thus we now have a grid 3 wide and 5 high.  Let's
    # read the actual data now.
    read grid data
    1 2 3
    2 3 4
    3 4 5
    4 5 6
    5 6 7
    # Now draw contours (automatically set; we could
    # have done `draw contour 2' to draw contour fro
    # value 2 or `draw contour 1 10 2' to draw contours
    # ranging from 1 to 10 with an increment of 2.)
    draw contour
    draw title "Example 4"