how to multiply one array of vector in another ?

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Amin Gan 2016-2-10

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/267508-how-to-multiply-one-array-of-vector-in-another

评论： Star Strider 2016-2-10

采纳的回答： Star Strider

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There are two same size vectors,A and B (1*2000 in size).

for each value of A must be used in equation below for all B values:

equation=A+A^2+B

for example:

A=[1 2 3]

B=[10 20 30]

I want following results:

 1+1^2+10 ,  1+1^2+20,  1+1^2+30
 2+2^2+10 ,  2+2^2+20,  2+2^2+30
 3+3^2+10 ,  3+3^2+20,  3+3^2+30

But, A and B both are 2000 in size, I expect to get 2000*2000 matrix for eqn.

can you please advise?

Thnks

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Answer 1

Star Strider 2016-2-10

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https://ww2.mathworks.cn/matlabcentral/answers/267508-how-to-multiply-one-array-of-vector-in-another#answer_209308

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Use bsxfun:

A=[1 2 3];
B=[10 20 30];
equation = bsxfun(@plus, (A'+A'.^2), B)
equation =
    12    22    32
    16    26    36
    22    32    42

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Amin Gan 2016-2-10

Thank you for your reply.

If I had a more complex equation such as:

eqn=A+sqrt(A^2-B), can I use bsxfun ?

thank you

Star Strider 2016-2-10

在 MATLAB Online 中打开

My pleasure.

Yes. You can ‘nest’ the bsxfun calls:

eqn = bsxfun(@plus, A', sqrt(bsxfun(@minus, A'.^2, B)));

or break them out into two or three lines to make them easier to read and (if necessary) troubleshoot:

eqn1 = bsxfun(@minus, A'.^2, B);
eqn2 = sqrt(eqn1);
eqn = bsxfun(@plus, A', eqn2)

Both produce:

eqn =
            1 +          3i            1 +     4.3589i            1 +     5.3852i
            2 +     2.4495i            2 +          4i            2 +      5.099i
            3 +          1i            3 +     3.3166i            3 +     4.5826i

The results are complex, because you’re taking the square root of negative numbers.

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