Using uint8 as matrix index

I have a matrix "parent" defined as uint32 type. Later, i use this parent to index another matrix

Counter(parent(2));

But i get the error 'Subscript indices must either be real positive integers or logicals.'

I have defined "Parent" as uint32 to save memory.

Answer 1

[the cyclist]

This code works perfectly fine for me:

A = uint32([4 5 6]);
idx = uint8(2);

A(idx)

It also works if idx is defined as a uint32.

Maybe you can post a code snippet that illustrates the error you are getting?

[Salman Gul]

In my case, counter itself is a uint8 type matrix...could that be an issue?

[the cyclist]

Shouldn't be a problem. My best guess is that you are accidentally trying to index with a zero, and the memory-saving integer situation is a red herring.

Answer 2

[Image Analyst]

See the FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_fix_the_error_.22Subscript_indices_must_either_be_real_positive_integers_or_logicals..22.3F

Chances are that the index is zero, or possibly negative.

[Salman Gul]

The issue is that if i let matlab define "parent" as double type by-default, the error is removed.

[Walter Roberson]

Is your code happening to try to store negative values for the counters? Does it arrive at the counters by doing subtractions that might happen to result in negative values?

Put a conditional breakpoint on the line

dbstop at LINENUMBER if parent(2) == 0

and run again and I suspect you will discover that the value is 0.

[the cyclist]

Salman, you now have 3 out of the top 10 contributors on this forum guessing at a solution. Can you please distill the simplest possible version of your code that will display this error, and post it? (Sometimes the distillation process itself will expose the error.)

Answer 3

[Image Analyst]

Note: parent and Parent are two different things because MATLAB is case sensitive. In your question you use it both ways and if you do that in your code, you will possibly have a problem. Do a case insensitive search for parent and make sure you're consistent in how you're using the letter case (capitalization).