How to compute the Laplace transform of a discrete signal?
This requires use of the MATLAB symbolic toolbox

&gt;&gt; syms x
&gt;&gt; f = x * cos(x);

&gt;&gt; t = linspace(0, 1000, 1000); % Or whatever values you want to evaluate the Laplace Transform over
&gt;&gt; L = double(laplace(f, t)); % Simulataneously compute the Transform and convert it from 'syms' to double


I guess this isn't exactly what you're asking for, as it requires keeping your function $f$ as a "symbolic expression". I dont know of any function which performs a "discrete Laplace tranform" though.

EDIT: Actually, I dont believe there is such thing as a Laplace Transform for discrete functions. However, the Laplace Transform is just a specific case of the z-Transform when $z = e^s$, which is definitely defined for discrete signals. Unfortunately I can't say much more about this relation between the two transforms, but hopefully this gives you a little more information about how to proceed from here.