#99 Provide a derivative and integral function in pgfmath

[student]

Some time ago there were two questions on TeX.sx of about how to plot the derivative of a function and how to plot the integral function numerically:

• http://tex.stackexchange.com/questions/73920/get-derivative-of-a-function/73924#73924
• http://tex.stackexchange.com/questions/103569/can-pgf-plot-the-integral-of-any-specified-function?lq=1

As suggested in a comment to the second question by Matthew Leingang, a simple solution just to provide the functions diff and int in pgfmath, as defined as follows:

diff(f(x)) = (f(x + h) - f(x))/h

where h is a small constant, say h = 0.001 by default.

Similar int should return the numerical integral. See Jakes answer in the second link for an example.

[Stefan Pinnow]

For details see https://github.com/pgf-tikz/pgf/issues/623