how to get following matrix using bsxfun

I have a matrix x=[0 0 0;5 8 0; 7 6 0].

I want a matrix m=[0 0 0; 5 8 0 ; 7 6 0 ; 0 0 8; 5 8 8; 7 6 8; 0 0 16; 5 8 16; 7 6 16] I want that the third column of matrix x gets multiplied each time by 8 while other two columns remain same. I want this to continue until the value in third column reaches 72. how can i do it with bsxfun??

Answer 1

[Geoff Hayes]

Saurabh - if x is your defined as

 x=[0 0 0;5 8 0; 7 6 0];

then you could replicate it 10 times as

 m = repmat(x,10,1);

then just replace the third column with

 m(:,3) = cell2mat(arrayfun(@(u)repmat(u*8,3,1),0:9,'UniformOutput',false)');

to produce the desired result. Try the above and see what happens!

[Ace_ventura]

Thanks Geoff.. It works Fine.

[Ace_ventura]

can it be done using bsxfun?? And what if i wanted to add certain constant to 1 and 2 column as well continuously throughout. Say addition of 5 throughout entire columnn1 and addition of 9 throughout entire column 2 with each repetition of matrix. Thanks in advance:)

[Geoff Hayes]

Saurabh - try the following

 x=[0 0 0;5 8 0; 7 6 0];
 cell2mat(arrayfun(@(u)x + repmat([u*5 u*9 u*8],3,1),0:9, 'UniformOutput',false)')

5, 9, and 8 are added to columns 1, 2, and 3 respectively of each new matrix. We use repmat to create the matrix to add to x at each iteration u. We apply this add using arrayfun for iterations 0 through 9. The result is a cell array, so we transpose the output from arrayfun and convert to a matrix using cell2mat.

Answer 2

[Andrei Bobrov]

k = 0:72/8;
M = repmat(x,numel(k),1);
add = 8*ones(size(x,1),1)*k;
M(:,3) = add(:);

with bsxfun

m = reshape(bsxfun(@plus,permute(x,[1 3 2]),...
            bsxfun(@times,reshape([0 0 1],1,1,[]),0:72/8)),[],3);

[Ace_ventura]

Thanks Andrei..Could u also answer my second question. what if i wanted to add a constant to column 1 and column2 with each matrix repetition. That is to say,if my constant to be added is 5 ,then my first column in second repetition of matrix is 5 10 12 and second column becomes 5 13 11. In third repetition first column becomes 10 15 17 and second column becomes 10 18 16 and so on. During this entire process my third column goes on with addition of 8 each time ( as u have answered)