Scilab function returning 2D matrix antidiagonal by index.

adiag.sci

//-->adiag([1 2 3 4; 5 6 7 8; 9 10 11 12],3)'
// ans  =
//    9.    6.    3.  

function [v] = adiag(x, z)
	// 2D matrix antidiagonal

	[N, M] = size(x)

	// The total diagonals count
	Z = N + M - 1
	// The current diagonal length
	z_len = min(z, Z - z + 1, min(N, M))

	i = max(z, N * (z - N + 1))
	step = N - 1
	v = x(i : step : i + step * z_len - 1)
endfunction