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Unable to perform assignment because brace indexing is not supported for variables of this type.

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Dear Matlab Community,
in a loop I am trying to write variables into a cell.
For variable sub_matrix it works, however for sub_matrix_idx it does not.
The error message:Unable to perform assignment because brace indexing is not supported for variables of this type.
The former are pixel values of an image in double format, the latter returns the position of these pixels on the image (also double, please see attached).
Any suggestions are appreciated
Levente Gellért
Levente Gellért on 10 Jan 2023
Dear Walter Robertson,
if I try to write sub_matrix_idx to a cell like I do witH "sub_matrices{1, index-1}=sub_matrix;"
I got the error message.
Image Analyst
Image Analyst on 10 Jan 2023
What does this show
whos sub_matrix
whos sub_matrices
I ran your code, drew a region, and it finished with no error. I tried several time.
But what are you trying to do? In words, rather than code. There might be a better way.
I attach some demos that might help.

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Accepted Answer

Walter Roberson
Walter Roberson on 10 Jan 2023
Your posted code has no indexed assignments to sub_matrix_idx so you need to post the code that you actually used.
I_idx=reshape (I_idx,[291,240]);
reshape() of a numeric is numeric.
() indexing of something numeric gives a numeric result.
So sub_matrix_idx is numeric, not cell. Using {} indexing to try to assign into it would be a mistake.
You could convert sub_matrix_idx into a cell using
sub_matrix_idx = num2cell(sub_matrix_idx);
but if you do, then watch out for your
if anynan(sub_matrix)==1
statement, as anynan() cannot operate on cell arrays.

More Answers (2)

Ryan Baird
Ryan Baird on 10 Jan 2023
It looks like sub_matrix is a matrix rather than a cell array, so it should be accessed with parenthesis:
sub_matrix(i, j) = ...
and not with braces:
sub_matrix{i, j} = ...

Levente Gellért
Levente Gellért on 11 Jan 2023
thanks for the helpful comments, now everything runs well.


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