MATLAB: Updating values in array based on index vector

array

Hi,

I have a 2D array (with zeros), and I want to update some indexes with 1's. I have a vectors with those indexes (seperatly for X and Y).

I can do a loop for i :Array(x(i),y(i)=1. but I'm looking for something more efficient (Run time is low, but probably I can do without loops)

Doing something like Array( X; Y ) = 1; is not doing what i'm looking for.

Any suggestions?

Thanks in advance 🙂

Best Answer

One of the ways is to convert your subscript to linear index and then do the assignments.

ind = sub2ind(size(A),x,y);
A(ind) = 1;

Related Solutions

MATLAB: Work with Array

Logical indexing can be a good way to remove or manipulate elements in an array. In your case, let's say you have an array of indices, some of which are invalid (i.e. less than 1):

ind = [1:10]-2

Create a new array of indices with only valid values:

validInd = ind(ind >= 1)

If you wanted to instead replace illegal index values with a number such as 1, you could do this:

 validInd = ind;
 validInd(validInd< 1) = 1

MATLAB: 2D logical indexing of 1D array for resulting 2D array

A = {'A';
    'B';
    'C'};
ind  = logical([1, 1; 0 0; 0 1]);
indD = double(ind) .* (1:numel(A)).';  % Auto-expand, >= R2016b
B    = cell(size(ind));
B(ind) = A(indD(ind))

Best Answer

Related Solutions

MATLAB: Work with Array

MATLAB: 2D logical indexing of 1D array for resulting 2D array

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