MATLAB: Performing without randperm function

matrix

from code below i get 10 matrix values,using randperm function,please can anyone tell how to perform without using randperm,
A=imread('dock.jpg');
A=rgb2gray(A);
A=imresize(A,[256 256])
A=double(A)
n = numel(A);
A1_10 = repmat(A,[1,1,10]);
t = ones(size(A));
for j1 = 1:size(A1_10,3)
p = t;
k = randperm(n);
k1=[1:n];
p(k(1:6000)) = 0;
A1_10(:,:,j1) = A1_10(:,:,j1).*p;
end
A1_10

Best Answer

A=imread('dock.jpg');
A=rgb2gray(A);
A=imresize(A,[256 256])
A=double(A)
n = numel(A);
A1_10 = repmat(A,[1,1,10]);
t = ones(size(A));
for j1 = 1:size(A1_10,3)
p = t;
p(randi(n,6000,1)) = 0;
A1_10(:,:,j1) = A1_10(:,:,j1).*p;
end
A1_10