What is an alternative FIND function that find indices and values of both ZERO and NONZERO elements in Matlab ?

Hello,

I am using Matlab and I would like to know how to find indices/values of both zero and nonzero elements of a given vector ? Can anyone help ?

For example:

X = [1 0 2; 0 1 1; 0 0 4];

How can I find indices of the elements in the first raw i.e. '1'; '0'; '2' ?

Thank you!

[Walter Roberson]

You want to know the indices of everything together regardless of the respective value? Or you want two outputs, one for the non-zero values and one for the zero values?

Are you looking for linear indices or for row and column indices?

[Kirby Fears]

Start here:

http://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html

[Gobert]

@Walter, @Kirby, Thanks for your replies. See this:

E = [2, 0, 5, 9];
k = 1: numel(E);
[i,j] = find(E(k))

The output is:

i =

       1     1     1

j =

       1     3     4

As can be seen, the (i, j) indices for 0 element in E are not provided. How can I also obtain the (i,j) indices for any 0 valued element that can be included (together with other nonzero valued elements) in E ? That's what I want to know.

Thanks again!

Answer 1

[Stephen23]

>> E = [2, 0, 5, 9];
>> [R,C] = ind2sub(size(E),1:numel(E))
R =
   1   1   1   1
C =
   1   2   3   4

Or using your original example:

>> X = [1 0 2; 0 1 1; 0 0 4];
>> [R,C] = ind2sub(size(X),1:numel(X))
R =
   1   2   3   1   2   3   1   2   3
C =
   1   1   1   2   2   2   3   3   3

or just the first row (as your question request) is very simple:

>> C = 1:size(X,2)
C =
   1   2   3
>> R = ones(size(C))
R =
   1   1   1

[Gobert]

Thank You!

Answer 2

[Image Analyst]

Try this:

X = [1 0 2; 0 1 1; 0 0 4]
[zeroRows, zeroColumns] = find(X == 0)
[nonZeroRows, nonZeroColumns] = find(X ~= 0)