I need to convert this experission into matlab code ( Integral Square Error )

[John D'Errico]

So what have you tried? If nothing, why not? Have you spent some time with the MATLAB onramp tutorial?

This is a simple integral, over a finite domain. So you might use tools like int, or integral. Or even trapz, depending on how your problem is formulated, and we are not told that.

Read the help for those tools. You will see examples in there of how to use them.