question about vector multiplication

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Judy Zhuo
Judy Zhuo on 7 Dec 2019
Answered: Sourav Bairagya on 10 Dec 2019
The Matlab vector v1 has a dimension of n-by-1 and the vector v2 has a dimension of 1-by-n, which of the following is true?
A) The+operation v1*v2 does+not+return+an+error
B) The+operation v2*v1 does+not+return+an+error
C) The+operation v1.*v2 does+not+return+an+error
D) None+of+the+above

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Answers (1)

Sourav Bairagya
Sourav Bairagya on 10 Dec 2019
The first two options of your question are performing matrix multiplication of the vectors A and B by considering them nX1 and 1Xn matrices respectively. In first case it will produce a nXn matrix and in 2nd case it will give 1X1 matrix i.e. a scalar.
In 3rd option, it is the case of element-wise multiplication.
C = A.*B performs the element-wise multiplication of vectors A and B, where either A and B are of same size or having compatible sizes. If A and B have compatible sizes, then the two vector implicitly expand to match each other.
Like, if one of them is a scalar, then the scalar is combined with each element of the other vector. Also, vectors with different orientations (one row vector and one column vector) implicitly expand to form a matrix. Hence, in these cases, this elememt-wise multiplications will sucessfully performed without throwing any error.
To know more about the compatible sizes of two vectors, you can leverage the following link:


Find more on Creating and Concatenating Matrices in Help Center and File Exchange


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