Hi I have the following piece of code: Code (Text): dataX = -4:1:4; dataY = [0 -1 -10 -40 -55 10 40 10 1]; figure(1) plot(dataX, dataY, '*'); x = -2:0.01:2; plot(-4:0.01:4, 1*conv(exp(-x).*heaviside(x),sin(x)), dataX, dataY, '*') mdl = @(a, x)(a(1)*conv(exp(-x).*heaviside(x),sin(x))); par=; [fitted_par, r, J, cov, mse] = nlinfit(dataX, dataY, mdl, par); What I am trying to do is to fit the function (a convolution) to the data set. However, I get an error due to vector size mismatch. I'm not sure what is going on here: The fitting routine should not care about how many data points I have? Regards, Niels.