how to return indices?

Hi,

I have a 3 dimensional data matrix (72*45*2109), and I need to extract all data less than 15. the final output should be a 3d matrix

I used the following lines, but the result is a vector. The point is to return the indices to have 3d matrix.

Any help would be greatly appreciated.

[r,c,v] = ind2sub(size(data),find(data >= 15));
l = data(sub2ind(size(data),r,c,v));

[DGM]

You get a vector, because those are the indices of elements that you wanted -- only the indices you wanted.

Arrays need to be rectangular, without holes.

With that restriction, you'll have to decide what you want to fill all the area where there are elements you didn't want. It could be zero, NaN, etc. It's up to you and what the subequent code can accept without causing errors, since neither zero nor NaN are valid indices.

[Lilya]

thanks for your comment

I've created an output nan matrix with the same dimension (72*45*2109), but all the output (r,c,v) are vectros as well

I don't know how to put them back in the output matrix

Answer 1

[Dyuman Joshi]

Based on your comment -

%random data
y=randi(30,2,3,4)

y = 
y(:,:,1) =

     7    17    10
    24    11    14


y(:,:,2) =

     3     2     6
    13    17     1


y(:,:,3) =

    26     3    14
    26    27     3


y(:,:,4) =

     7     5     4
     3     7    26

z=NaN(2,3,4);
z(y<15)=y(y<15)

z = 
z(:,:,1) =

     7   NaN    10
   NaN    11    14


z(:,:,2) =

     3     2     6
    13   NaN     1


z(:,:,3) =

   NaN     3    14
   NaN   NaN     3


z(:,:,4) =

     7     5     4
     3     7   NaN

[Lilya]

Thank you very much!!

perfectly worked.