How can I put in a triangle into a matrix?

I have the matrix

A=zeros(100,100) I want to create an equilateral triangle with top vertex at point 50 (right in the middle of the matrix) extending down a total height of 10 array entries in height.

I there a function that can do this?

Thanks

Answer 1

[Image Analyst]

This will do it:

% Define vertices coordinates.
x = [50, 40, 60]
y = [50, 60, 60]
% Make triangle.
A = poly2mask(x, y, 100, 100) % Last two arguments are # of rows and columns.

Answer 2

[Matt J]

If you don't have the Image Processing Toolbox, you can do it with inpolygon

    [I,J]=ndgrid(1:100);

    Iv=[50,60,60];
    Jv=[50,40,60];

    Image=inpolygon(I,J,Iv,Jv);