Matlab: Change elements in 3D array using given conditions

Question

I have a 3 dimensional array (10x3x3) in Matlab and I want to change any value greater than 999 to Inf. However, I only want this to apply to (:,:,2:3) of this array.

All the help I have found online seems to only apply to the whole array, or 1 column of a 2D array. I can't work out how to apply this to a 3D array.

I have tried the following code, but it becomes a 69x3x3 array after I run it, and I don't really get why. I tried to copy the code from someone using a 2D array, so I just think I don't really understand what the code is doing.

A(A(:,:,2)>999,2)=Inf;
A(A(:,:,3)>999,3)=Inf;

Divakar · Accepted Answer · 2015-02-26 12:02:25Z

3

One approach with logical indexing -

mask = A>999;  %// get the 3D mask
mask(:,:,1) = 0; %// set all elements in the first 3D slice to zeros, 
%// to neglect their effect when we mask the entire input array with it
A(mask) = Inf %// finally mask and set them to Infs

Another with linear indexing -

idx = find(A>999); %// Find linear indices that match the criteria
valid_idx = idx(idx>size(A,1)*size(A,2)) %// Select indices from 2nd 3D slice onwards
A(valid_idx)=Inf %// Set to Infs

Or yet another with linear indexing, almost same as the previous one with the valid index being calculated in one step and thus enabling us a one-liner -

A(find(A(:,:,2:3)>999) + size(A,1)*size(A,2))=Inf

edited Feb 26, 2015 at 12:02

answered Feb 26, 2015 at 11:50

Divakar

222k19 gold badges273 silver badges374 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

emmalgale Over a year ago

Thanks. They all worked brilliantly. I especially like the one-liner!

Divakar Over a year ago

@emmalgale Me too! Exploring through the approaches led to that final one!

Collectives™ on Stack Overflow

Matlab: Change elements in 3D array using given conditions

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related