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Matlab `image(image)=-1`?

I'm really new at matlab and I'm trying to understand this piece of code:

mask = false(size(image_map));
image_map(mask) = -1;

I understand that the first line is to create an array of logical zeros that is the same size as image_map, but what is this image_map(mask) for?

Sorry if it's a dumb question and the answers will be appreciated.

Solution

  • In matlab you may access entries of a matrix is several ways. One is by linear indexing:

    image_map( 4 ) % access the fourth element of image_map

    However, there is a more efficient way, using logical indexing.
    In this approach you create a logical matrix, the same size as image_map and then you can access all the extrines in image_map for which the locial matrix has the value true.