How do I rotate a square (rectangle) to make a diamond?

I'm trying to rotate a purple square into a purple diamond. I am working with PsychToolBox and a template of code that already successfully draws a purple square. How do I rotate the square 45 degrees to make a diamond using a format similar to the one used in the code for a square? I've included the relevant parts of the code below, but I am pretty new to MatLab and working with a very large script so I may have missed something.

Image of Code attached

Answer 1

[Walter Roberson]

The closest I can find in Psychtoolbox is FramePoly. You would need the points of the polygon vertex. Those are not difficult to calculate for the case of a square rotated 45 degrees:

sq = sqrt(2);
x = [sq, 0, -sq, 0, sq]
y = [0, sq, 0, -sq, 0];