Error using accumarray First input SUBS must contain positive integer subscripts.

Question

Asliddin Komilov 2019-9-14

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/480366-error-using-accumarray-first-input-subs-must-contain-positive-integer-subscripts

回答： Walter Roberson 2019-9-15

testdata.mat

I am very much troubled solving this:

>> [X, Y, Z]=ndgrid(x,y,z);
>> C = round(ceil(Y./Z));
>> N = accumarray([X(:), C(:)], M(:));

Error using accumarray

First input SUBS must contain positive integer subscripts.

data file attached

I have already read all questions and answers about it here, cant figure out whats wrong.

thanks

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Answer 1

Stephen23 2019-9-14

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https://ww2.mathworks.cn/matlabcentral/answers/480366-error-using-accumarray-first-input-subs-must-contain-positive-integer-subscripts#answer_391847

"I have already read all questions and answers about it here, cant figure out whats wrong."

After reading many answers, you should know by now that indices must be positive integers.

Now take a look at your x data:

How many of those values are positive integers? How many of those values can be used as indices?

Yet you try to use X (which simply contains values from x) as indices.

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Asliddin Komilov 2019-9-15

will you so be kind to take a look to this question:

https://www.mathworks.com/matlabcentral/answers/480253-how-to-change-axis-of-a-matix

Stephen23 2019-9-15

编辑：Stephen23 2019-9-15

@Asliddin Komilov : that is a different question. I will take a look at your other question.

As far as I can tell, I have answered the question that you asked at the top of this page (which was "what is wrong with my code?").

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Answer 2

Walter Roberson 2019-9-15

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https://ww2.mathworks.cn/matlabcentral/answers/480366-error-using-accumarray-first-input-subs-must-contain-positive-integer-subscripts#answer_391909

You also posted this in

https://www.mathworks.com/matlabcentral/answers/480253-how-to-change-axis-of-a-matix#comment_745999

and I gave a complete code solution there.

Your question there that led me to create that code for you had been strictly positive integers, but it turned out that your real data involved negatives for Z, and involved 0 as well as positive integers for Y, and involved real-valued X from 0 to 1. Those are quite different conditions that should have been stated ahead of time.