Example

This example compares the data in the file population.dat to a theoretical curve:

        pop(x) = 103*exp((1965-x)/10)
        plot [1960:1990] 'population.dat', pop(x)

The file population.dat might contain:

        # Gnu population in Antarctica since 1965
        1965   103
        1970   55
        1975   34
        1980   24
        1985   10

A simple example of plotting a 3-d data file is

        splot 'glass.dat'

where the file datafile.dat might contain:

        # The valley of the Gnu.
        0 0 10
        0 1 10
        0 2 10

        1 0 10
        1 1 5
        1 2 10

        2 0 10
        2 1 1
        2 2 10

        3 0 10
        3 1 0
        3 2 10

Note datafile.dat defines a 4 by 3 grid ( 4 rows of 3 points each ). Rows are separated by blank lines.

Note also that the x value is held constant within each isoline. If you instead keep y constant, and plot with hidden-line removal enabled, you will find that the surface is drawn 'inside-out'.

Actually it is not necessary to keep the x values constant within an isoline, nor is it necessary to keep the y values the same along the perpendicular isolines. gnuplot requires only that the number of points be the same along each isoline.