from Power Spectrum Estimation (non-parameteric methods) by payam masoumi
there is a simple demo for non parameteric spectral estimation methods

nwhite(x)
function temp = nwhite(x)

global sigtype;
global vari;

sigtype = 1;
HH = findobj(gcf,'Tag','white_var');
vari = str2num(get(HH,'String'));
if ~vari
    vari=0;
end

Contact us at files@mathworks.com