[angie]

ok啦
function sort_a_matrix
clear
clc
X=rand(4,5)
[m,n]=size(X);
max_number=10;
max_value=sort(reshape(X,1,m*n),'descend')
max_value=max_value(1:max_number)
% max_site(m,n)=zeros
for i=1:max_number
[r(i),c(i)]=find(X==max_value(i));
end