Assignment has more non-singleton rhs dimensions than non-singleton subscripts

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mathn00b 2017-7-12

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评论： Walter Roberson 2017-7-13

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Can someone help me with this expression and the following error message?

Expression:

A(i:n, i)=(A(i:n, i-1) - A(i-1:n-1, i-1)) ./ (x(i:n) - x(1:n-i+1));

Error Message:

Assignment has more non-singleton rhs dimensions than non-singleton subscripts

I cannot find the reason, why Mathlab is complaining.

Thanks in advance for helping me :)

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dpb 2017-7-13

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Show us what

whos A x

returns as well i, n.

Then try

tmp=(A(i:n, i-1) - A(i-1:n-1, i-1)) ./ (x(i:n) - x(1:n-i+1));

without the assignment and then what is

whos tmp % ?

That should answer the question. I'm guessing there's an implicit expansion going on from a combination of a column (A reference) and row (x reference) but I can't test what happens in later releases here after implicit expansion was implemented...

Walter Roberson 2017-7-13

dpb is correct. If x is a row vector then (x(i:n) - x(1:n-i+1)) would be a row vector. (A(i:n, i-1) - A(i-1:n-1, i-1)) would be a column vector. If you are using R2016b or later, combining a row vector and a column vector with ./ would get you a 2D array as a result.

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