Zero a cell matrix with varying number of zeros

Hi,

I have a cell matrix, C, that's n x n, and an array A of size n x 1. The entries of array A dictate the no. of column of zeros in the matrix M.

i.e. M1 has a dimension 6 x A(1), M2 has a dimension 6 x A(2)

Given an index i, what I wish to do is the following,

Column i of C is filled with matrix Mi of dimension 6xA(i). So all n entries in column i are replaced with a matrix of zeros.

I know the following code

C(:,:) = {zeros(3,3)}

will give me zeros eveyrwhere, I want to leverage similar syntax to solve my problem. Avoiding the use of for loops.

Thank you.

Answer 1

[ME]

I'm not 100% sure I follow, but as I understand you want to take some list of columns and turn all elements in that column to zeros?

If so then you could use something like:

C(:,cols) = 0

where cols is an array containing the indices of the columns to be zeroed. For example setting cols = [1 3] would put zeros in the first and thrid columns.

If that's not what you meant then please could you explain some more?

[Mohammed Kagalwala]

Ah sorry not what I meant.

for example, A = [3,4,6]

Then I want each entry of column 1 of C to be filled with a matrix of zeros of dimension 6x3. Next I want each entry of column 2 of C to be filled with a matrix of zeros of dimension 6x4, and so on.

Hope this helps.

[ME]

So if you start with C = [1 2 3 4; 5 6 7 8; 9 10 11 12] and A = [3 4 6] then you'd end up with something like [0 0 0 0 0 0 0 0 0 0 0 0 0 4; 0 0 0 0 0 0 0 0 0 0 0 0 0 8; 0 0 0 0 0 0 0 0 0 0 0 0 0 12]?

[Mohammed Kagalwala]

C is going to be initialized as an empty cell of size n x n.

[ME]

Ok, but the size of C will increase when you apply your method?

[Mohammed Kagalwala]

C is a cell of a fixed size nxn. Each cell column will have a unique size based on A. i.e. something like this,

In this case A = [5 1 5 10 8 8 8 8 9 8 10 2].

This was however created using a for loop. I want to make this same cell structure without the use of for loops.

[ME]

Oh, I see! Sorry, I completely missed the fact you wanted to do this inside a cell array. I don’t have a good answer for you right now but I’ll have a think on it.