You can graph with Desmos . Here's an example: https://www.desmos.com/calculator/xrfmngtyoi . The syntax for defining a piecewise function should be clear from the example above, but to be explicit: f(x) = {[condition 1 on x]: [expression 1], [condition 2 on x]: [expression 2]}. The absolute value function over the reals would then be f(x) = {x >= 0: x, x < 0: -x} After defining your piecewise functions, plot the composition by adding the equation of that graph, i.e., if you've defined f and g, add the equation y = f(g(x)) or y = g(f(x)) to see the composition. Answer from 355over113 on reddit.com