Comments on: MATLAB Basics video: Absolute and Logical indexing

By: Doug

Doug — Mon, 08 Mar 2010 16:27:04 +0000

@ronny

>> a = [2 0 3; 0 4 0]

a =

     2     0     3
     0     4     0

>> b = (a>1)

b =

     1     0     1
     0     1     0

>> c = find(a>1)

c =

     1
     4
     5

Try this. If you must use find, you could always make a zeros matrix of the same size and set the indices that you find to 1.

By: Ronny

Ronny — Wed, 03 Mar 2010 19:49:48 +0000

Hi Doug,
I saw your video and I have a question, when I use “find” with a matrix with X,Y,Z or logical for extract valor from ranges, the new matrix is always a column vector and I need this matrix in similar format (x,y,z), how can I do?
Please let me know,
Thanks,
RM

By: Doug

Doug — Mon, 03 Mar 2008 19:20:21 +0000

It will be required to pull out the intermediate values to use that logical matrix or you will need to do some other indexing method.

Doug

By: Dennis Olly

Dennis Olly — Sun, 02 Mar 2008 00:12:00 +0000

Hi Doug, very clear video, however, is it possible to do logical indexing directly to a submatrix, eg:

data=zeros(10,10,10);

here data(:,:,5) could be slice.
now let

mask=zeros(10,10);mask(5:5,8:8)=1;

Is it possible to use this mask to logically index the submatrix data(:,:,5)?

slice = data(:,:,5);
and then accessing slice(mask) is possible. But can this not be done directly, without extracting ‘slice’?

Thanks
Dennis

By: naor

naor — Thu, 06 Sep 2007 22:51:49 +0000

Doug, in the RSS feed of your blog, read in internet explorer 7, the videos never show. I don’t mean they don’t run, there are just lines of text with a single blank line where the videos should be. Is there a way to fix this?
Thanks,
naor (win32xp r2006a)