Help with integral2 calculator

As always, my pleasure.

That becomes a bit more complicated, because you must test for a numeric input, and if it’s not numeric, then use str2func:

ymax = input('enter upper y boundary = ','s')
n = str2double(ymax);
if isnan(n)
    ymax = str2func(['@(x) ' vectorize(ymax)]);
else
    ymax = n;
end

You’ll need to do this in each limit, or at least those for which you expect a function input.