The function ztrans finds the Z transformation of f(n) with respect to z. Formally,

ztrans recognizes and specially handles a large class of expressions, and only resorts to using the definition to calculate the transformation if the given expression has an unknown form. If the Z transform of the given expression cannot be found in a closed form, then the left-hand side of the formal definition is returned, rather than the right-hand side.

The functions referred to in the literature as Delta and Step may be simulated in this function as charfcn[0](...) and Heaviside(...), respectively.