Question about intwave and cwt function of Wavelet Toolbox

Hello everyone,

I am wondering why we need to take integrate of the wavelet function (using intwave) before doing continuous wavelet transform. And why in cwt function, we need to differentiate the convolution like the following:

coefs(ind,:) = -sqrt(a)*wkeep1(diff(wconv1(ySIG,f)),lenSIG)

I copy the above line from the code implementing cwt function. It's quite confusing for me since it doesn't look like what I read and understand from mathematical formula of continuous wavelet transform.

I appreciate any comment/feedback.

Thank you for your help, Linh