Convert Index values from "find" function into coordinates.

Hello! I am using the find function in my code. If I want to find where all the 2's are in a matrix, suppose, this function will spit out the indices of all the 2 values, but it does so in an interesting way:

a =

     1     1     2     1
     1     1     1     1
     1     1     2     1
     1     2     1     1

Now, if I implement the function, find(a==2), I get:

ans =

     8
     9
    11

Notice how it counts down each row until it reaches a 2. I would like a coordinate instead; I would like a (row,column) coordinate. Any ideas on how I can do this using the find function?

Much appreciated! Sean

Answer 1

[Jan]

When you have a question concerning a specific command, reading the corresponding docs helps. See doc find :

[row, col] = find(a == 2)

:-)

[Sean Farrell]

Ahh yes! I actually used this [row,col] feature of the find function the other day. I just did not connect it to this problem. Thank you very much!

[Jan]

You are welcome.

[Daniel Garside]

Is there a neat way to do this for n-dimensional arrays?

(I feel like I've seen a trick somewhere but can't find it again...)

[Stephen23]

@Daniel Garside: use ind2sub:

[R,C,P,...] = ind2sub(size(A),find(A==2))

[Jos (10584)]

And without specifying the number of dimensions:

[subI{1:ndims(A)}] = ind2sub(size(A), find(A==2))