MATLAB placing integer at wrong index

Question

I have a 3d matrix of size(7,24,7) , what I am trying to do is find all the indexes of matrix(:,:,2) which are less 1 and replace those indexes in matrix(:,:,7) as 1 The matrix(:,:,2) looks somethings like this

Columns 1 through 13

   NaN       NaN       NaN       NaN       NaN       NaN       NaN       NaN         0    3.2146    3.4017    4.1404    4.1567
   NaN       NaN       NaN       NaN       NaN       NaN       NaN   12.7279       NaN         0    3.5119    3.4034    4.0415
   NaN       NaN       NaN       NaN       NaN       NaN    0.5000         0   13.4483   13.0618   11.4976   12.7435   12.0439
   NaN       NaN       NaN       NaN       NaN       NaN    0.5175         0       NaN    2.7080    5.9442    4.5981   14.4535
     0         0       NaN       NaN       NaN       NaN    0.5774       NaN   12.0000   10.7083   14.5308   15.5869   14.1067
   NaN       NaN       NaN       NaN       NaN       NaN       NaN       NaN       NaN       NaN       NaN       NaN       NaN
   NaN       NaN       NaN       NaN       NaN       NaN       NaN         0       NaN       NaN       NaN       NaN       NaN

Columns 14 through 24

    3.7342    3.0119    2.8785    2.0736    1.4142    2.8284         0       NaN       NaN       NaN       NaN
    3.1623    3.8173    3.8297    6.8981    9.1788    9.1287    8.5781    7.8951    3.7859       NaN       NaN
    9.2402    6.8328    6.8874   11.2933   16.5555   17.5816   16.9247   14.8052    9.0701       NaN       NaN
   15.3199   13.0767   12.2584   10.8546   11.5016   11.1679   10.7414    7.5572    7.1201       NaN       NaN
   13.1808   11.8533    7.2023   11.7163   12.9769   12.3000   10.7779   10.6315    5.1769       NaN       NaN
       NaN       NaN       NaN       NaN       NaN       NaN       NaN       NaN       NaN       NaN       NaN
       NaN       NaN       NaN       NaN       NaN       NaN       NaN       NaN       NaN       NaN       NaN

What I tried was

[I,J] = ind2sub([7,24],find(matrix(:,:,2) <=1))

The I and J values I received are accurate

I =

 5
 5
 3
 4
 5
 3
 4
 7
 1
 2
 1

J =

 1
 2
 7
 7
 7
 8
 8
 8
 9
10
20

but when I convert these indices to values 1 I get the 1s at the wrong indices, does anyone have any idea what am I doing wrong ?

 matrix(I,J,7) = 1

matrix(:,:,7) =

Columns 1 through 22

 1     1     0     0     0     0     1     1     1     1     0     0     0     0     0     0     0     0     0     1     0     0
 1     1     0     0     0     0     1     1     1     1     0     0     0     0     0     0     0     0     0     1     0     0
 1     1     0     0     0     0     1     1     1     1     0     0     0     0     0     0     0     0     0     1     0     0
 1     1     0     0     0     0     1     1     1     1     0     0     0     0     0     0     0     0     0     1     0     0
 1     1     0     0     0     0     1     1     1     1     0     0     0     0     0     0     0     0     0     1     0     0
 0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0     0
 1     1     0     0     0     0     1     1     1     1     0     0     0     0     0     0     0     0     0     1     0     0

Columns 23 through 24

 0     0
 0     0
 0     0
 0     0
 0     0
 0     0
 0     0

Answer 1

Just try

[I,J] = ind2sub([7,24],find(matrix(:,:,2) <=1));
matrix(sub2ind([7,24,7],I,J,7*ones(length(I),1))) = 1;

You need to access the table with linear indexing.

Answer 2

This is how indexing works in MATLAB. Read more here.

To circumvent that problem you can use linear indices.

You can get the linear indices of the subscripts that you want by:

linind=sub2ind(size(matrix),I,J,7*ones(size(I)));

And access those ones (and replace by 1) by:

matrix(linind)=1;