fold2.m

为stanford大学donoho教授所编写的redgit变换源代码。是用c编写的

function xd = fold2(x)
% FOLD2  Folding a matrix

[m, n] = size(x);

I = [1:m, m:-1:2];
J = [1:n, n:-1:2];

xd = x(I, :);
xd = xd(:, J);