[MATLAB图像处理] matlab 问题

[qqguoguilia]

% SUBMAT
%
% Function to extract the i'th sub-matrix 'cols' wide from a large
% matrix composed of several matricies. The large matrix is used in
% lieu of an array of matricies

function a = submat(big,i,cols)

a = big(:,((i-1)*cols+1)i*cols));



请各位帮忙看看这段代码是什么意思啊，我很苦恼，不胜感激！！！