! Demo about plotting functions.
! Author: Francois Tonneau

size 10 7

set font ss

! We use a 'begin graph ... end graph' block to plot two simple mathematical
! functions.

begin graph

    ! The effect of the 'math' command is that axes cross at point (0, 0) and
    ! that axis ticks extend on both sides of the axis.

    math

    ! Regardless of the 'math' command, there are many ways to customize axes
    ! in GLE. Here we specify the minimum, maximum, and numerical distance
    ! between ticks for the x axis. We also specify tick length and remove
    ! subticks from all axes. Anything about axes that is not customized
    ! assumes default values.

    xaxis min -3 max 3 dticks 1
    ticks length 0.08
    subticks off

    ! The 'let' command allows us to define datasets as mathematical functions
    ! (i.e., expressions of x) instead of values loaded from a data file. The
    ! defining expressions may include parentheses and usual math operators,
    ! but must be written without spaces.

    let d1 = (1/4)*(x^2)
    let d2 = 3*sin(x)

    ! Now we can plot our previously defined datasets:

    d1 line color cadetblue lwidth 0.03
    d2 line color indianred lwidth 0.03

end graph

! We add descriptions of our functions to the plot. GLE has a variety of text
! formatting operators, such as the '^{...}' operator to produce superscript:

amove 0.6 5.6
write "y = 0.25 x^{2}"

amove 6 6.25
write "y = 3 sin(x)"

! Done. We have learned about function plotting and about the math mode of axis
! customization.