How can I do the following integration/differentiation in matlab to end up with $f(z)$?
$$ f(x;df,ncp) = ncx2pdf(x, df, ncp), \quad\text{where ncx2pdf is the non-central chi-square distribution function}\\ f(z;n,\lambda) = \frac{\partial}{\partial z}\left[\int_{0}^{\infty}\int_{0}^{y+z}f(x;n,\lambda)f(y;n,\lambda) dx dy\right] $$