How to make matrix for points according to an expression

Question

I have n 2-D circles represented by their radii and coordinates of centers. So, I have nx3 matrix [centers, radii].

I want to create nxn matrix A so that A(i,j) = max(radii(i),radii(j)). I thought it's easy problem but unexpectedly stuck with it.

Answer 1

You can use bsxfun with the built-in @max that takes care of the expansion onto a n x n array and then does the max finding for each pair of elements. Here's the code -

A = bsxfun(@max,radii,radii.')