Elementwise Multiplication (Dot Multiplication) of Matrices
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Chuck on 24 Mar 2018
Commented: Star Strider on 24 Mar 2018
I am an instructor of MATLAB at a university. And we traditionally taught that for element-wise multiplication to work, both dimensions (row and column number) of each matrices must be exactly the same. For instance, you could multiply a 1x3 array with another 1x3 array, but not with a 4x1 array. And it used to be like that, otherwise, it would give an error, saying "matrix dimensions must agree".
I just noticed that at least in MATLAB 2017a, you actually can multiply various sizes of arrays element-wise. For example, you can multiply a 1x3 array with a 4x1 array, getting a 3x4 array. However, you still cannot element-wise multiply a 1x3 array with a say, 2x2 array. What is the rule for the dimensions when doing elemnent-wise multiplication there? And in which edition of MATLAB this change occurred?
It’s called ‘implicit expansion’, and was introduced in R2016b.
I can’t find a specific link to it. You can find it under Mathematics in the Release Notes (link) for R2016b.
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