Creating a Piecewise Symbolic function

hello!

I need help creating a piecewise function out of 2 symbolic functions. I have:

a = poly2sym(polyfun); %Convert to symbolic

b = poly2sym(polyfun1); %Convert to symbolic

Now I want to create a function f, that is the piecewise composition of a and b. I can use the heavisde function for regular numeric functions like this:

j = '(heaviside(x)-heaviside(x-1))'*x.^2;

But the above is a numeric expression. If I try to make mine numeric by doing:

j = '(heaviside(x)-heaviside(x-1))'*matlabFunction(a)

It returns an error about using "mtimes". A and b are both symbolic, and I need j to be pieciewise and also symbolic. Any ideas?

thanks in advance!

Answer 1

[Walter Roberson]

'(heaviside(x)-heaviside(x-1))'*x.^2 means the string '(heaviside(x)-heaviside(x-1))' matrix-multiplied by the element-wise square of x.

Anything in quotes is a string, not symbolic.

Also, matlabFunction() returns a function handle, not a symbolic function.

syms x
(heaviside(x)-heaviside(x-1)) * a

would be a symbolic expression. You could matlabFunction() the result, I suppose.