matlab,sum,continuous-integration,convolution,fourier-descriptors

That is because conv is only defined for numeric inputs. If you want to find the convolution symbolically, you'll have to input the equation yourself symbolically using integration. If you recall, the convolution integral is defined as: Source: Wikipedia Therefore, you would do this: syms x tau; F = int(h(tau)*x1(x-tau),'tau',-inf,+inf);...