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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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?
3 commentaires
Bruno Luong
le 18 Sep 2018
Modifié(e) : Bruno Luong
le 18 Sep 2018
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
>>
Réponses (2)
dpb
le 16 Sep 2018
Modifié(e) : dpb
le 16 Sep 2018
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.
9 commentaires
Bruno Luong
le 17 Sep 2018
Modifié(e) : Bruno Luong
le 17 Sep 2018
there is inplaceprod.c C-file that allows to perform inplace element-wise product of vector via MEX.
You'll be careful to use such inplace operation since it is not meets MATLAB specification and can produce unexpected side effect.
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