Find the index of specific values in my matrix

Hi,

I have a matrix with zeros and ones and I want to find the index of every one in my matrix and give the index in two vectors. One vector for the x-index and one for the y-index.

This is my matrix:

A = [0 0 1 0 1 0 
     1 0 1 0 0 1
     1 0 1 0 1 0]

size is 3x6

Then I need a vector where the x-position all ones in the matrix is given and another vector where the y-position of all ones in the matrix is given.

I used the find command for my issue but it gives me just the first 1 or the last 1.

And I also tried to wirte a loop:

row=[];
col=[];
for x=1:3
    for x=1:6
        if A(x,:)==1;
            row(y)=x;
            col(y)=y;   
        end
    end
end

But without success.

I need these two vectors because I want to plot the matrix.

And the way I think to do it is with the command plot. For that I need the vector with the indexes.

plot(row,col

I hope you understand my issue and can give me a hinte.

Thanks

Best Pouyan

Answer 1

[Scott MacKenzie]

No need for loops. Just use the ind2sub function:

A = [0 0 1 0 1 0 
     1 0 1 0 0 1
     1 0 1 0 1 0]
 
[x, y] = ind2sub(size(A), find(A==1))

Output:

A =

0 0 1 0 1 0

1 0 1 0 0 1

1 0 1 0 1 0

x =

2

3

1

2

3

1

3

2

y =

1

1

3

3

3

5

5

6

[Pouyan Sadeghian]

Hi Scott,

thanks for your answer. I did not know this command. Very useful.

Thanks!

best