The well-known min function can operate along either the rows or the columns of a matrix by using
[Y,I] = min(X,,1) or [Y,I] = min(X,,2)
but it cannot operate along a diagonal dimension. For this problem, create a function that returns the smallest component along each diagonal of a matrix (starting with the one-element diagonal in the bottom left corner of the matrix).
X = magic(3) = [8 1 6 3 5 7 4 9 2]
Y = mindiag(X) = [4 3 2 1 6]
See also maxdiag.