Is there a function that performs element by element multiplication between two variables and stores in one of the variable by default?

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D_coder 2018-9-16

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https://ww2.mathworks.cn/matlabcentral/answers/419283-is-there-a-function-that-performs-element-by-element-multiplication-between-two-variables-and-stores

编辑： Bruno Luong 2018-9-18

在 MATLAB Online 中打开

I want to do this operation

A = A.*B;

Is there a function

func(A, B)

that multiplies A and B and saves the result in A? If not how do we create such a function?

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D_coder 2018-9-16

because i want to use it in a function as an argument directly inside a loop that runs about 10K times

Bruno Luong 2018-9-18

编辑：Bruno Luong 2018-9-18

在 MATLAB Online 中打开

It seems MATLAB (at least with R2018b) is intelligent enough to do inplace product when calling A=A.*B as shows bellow (the pr address is dd885ac0 and does not change after calling mtimes):

>> format debug
>> a=rand(1,3)+1i*rand(1,3)
a =
Structure address = d743b820
m = 1
n = 3
pr = dd885ac0
     0.9572 + 0.1419i   0.4854 + 0.4218i   0.8003 + 0.9157i
>> b=rand(1,3)+1i*rand(1,3)
b =
Structure address = d743b890
m = 1
n = 3
pr = de61eb00
     0.7922 + 0.0357i   0.9595 + 0.8491i   0.6557 + 0.9340i
>> a = a .* b
a =
Structure address = d743b820
m = 1
n = 3
pr = dd885ac0
     0.7532 + 0.1466i   0.1076 + 0.8168i  -0.3305 + 1.3479i
>> c = a .* b
c =
Structure address = d743bd60
m = 1
n = 3
pr = 2ea50160
     0.5915 + 0.1430i  -0.5904 + 0.8751i  -1.4757 + 0.5752i
>>

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回答（2 个）

dpb 2018-9-16

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编辑：dpb 2018-9-16

在 MATLAB Online 中打开

Sure, there's a function for virtually everything in Matlab...all operators are are aliases for the underlying functions.

>> help times
.*  Array multiply.
  X.*Y denotes element-by-element multiplication. ....
...
A=times(A,B);

is functional form for A.*B but that's as far as you can get towards the Q?.

There is no syntax that supports in-place storage into one of a function's actual arguments as you're asking for. You can only store results of a function return to an assignable object on the LHS of an expression or use the results in an expression.