How can you plot chromaticity diagrams using MATLAB using xyz values or L*a*b*?

How can you plot chromaticity diagrams using MATLAB using xyz values or L*a*b*.

I want the diagrams to look something like this: http://en.wikipedia.org/wiki/File:CIE1931xy_blank.svg

More information can be found here: http://en.wikipedia.org/wiki/CIE_1931_color_space

So far I have:

>> x = x_bar./(x_bar + y_bar + z_bar);
>> y = y_bar./(x_bar + y_bar + z_bar);
>> plot(x,y)

I appreciate any help you can give me. Thank you.