Multiply each item of an array with every item of another array

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Christoph Meier 2016-2-29

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https://ww2.mathworks.cn/matlabcentral/answers/270702-multiply-each-item-of-an-array-with-every-item-of-another-array

评论： Image Analyst 2018-10-19

采纳的回答： Image Analyst

Dear matlab community,

I have a relatively simple problem:

I have two arrays, say:

and

I would like to multiply each of the first vector items with every of the second vector items, and print a new vector, which gives the output:

1*10

1*11

1*12

2*10

2*11

2*12

3*10

3*11

3*12

Thank you very much, I appreciate your help!

Greetings from Australia,

Chris

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采纳的回答

Image Analyst 2016-2-29

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/270702-multiply-each-item-of-an-array-with-every-item-of-another-array#answer_211743

在 MATLAB Online 中打开

Like this:

m1 = [1;2;3]
m2 = [10;11;12]
out = m1 * m2'
% Make into column vector
out = out(:)

I'm sure there are probably other ways.

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Martin Adams 2018-10-19

It seems like it is fairly easy to run out of memory when doing this with large arrays! I tried to do this with two 90k-long vectors! How much memory would be needed?

Image Analyst 2018-10-19

在 MATLAB Online 中打开

>> bytes = 90000*90000*8
bytes =
               64800000000
>> gigaBytes = bytes / 1e9
gigaBytes =
                      64.8

And you'd have two arrays so that would be 129 GB. That's a fair amount. You probably don't have that much spare RAM.

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