MATLAB Basics video: Absolute and Logical indexing

This is one in a series of videos covering MATLAB basics. It is meant for the new MATLAB user.

This video covers how to use row and column notation to be able to pull a subset of data from a larger matrix. This is a basic skill that is required for anyone that is going to use MATLAB. This particular type of indexing is less intuitive than the mat(row,col) indexing, it deals with using a single value as an index into a matrix like mat(ind) and mat([0 1 0 0 1]). These are also very important techniques for indexing into MATLAB.

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3 Responses to “MATLAB Basics video: Absolute and Logical indexing”

naor replied on September 6th, 2007 at 5:51 pm :

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)

Dennis Olly replied on March 1st, 2008 at 7:12 pm :

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

Doug replied on March 3rd, 2008 at 2:20 pm :

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

About

Doug Hull is an Application Engineer at The MathWorks. A MATLAB user since 1994, he gets paid to live, eat, and breathe MATLAB! This blog is dedicated to promoting the File Exchange by highlighting files and original video content.

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September 6th, 2007