Understanding the difference between normal multiplication between two vectors and multiplication with dot operator.

Hello all, I am trying to understood the difference between normal multiplication and mutliplication with dot operator in caseof two vectors.

For example,

If we have two vector H of dimension 2 X 4 and B of dimension 4 X 1 then writing

Y = H*B % ---(1)

do not cause any error.

But if we write

Y = H.*B %--- (2)

then it gives the following error: Arrays have incompatible sizes for this operation.

Any help is highly appreciated.

[Dyuman Joshi]

@chaaru datta, refer to Array vs Matrix Operations

Element-wise multiplication can be done for arrays of uneqal size as well -

x = rand(1,3);
y = eye(3);
z = x.*y

z = 3×3

0.5588 0 0 0 0.5351 0 0 0 0.3084

The necessity for this it to have compatible size - Compatible Array Sizes for Basic Operations

Edit - @Stephen23, thanks for the correction, I have updated my comment.

[Stephen23]

"the second case is explained here"

No, element-wise array multiplication is definitely not explained by the DOT documentation.

However it is explained by the TIMES documentation:

https://www.mathworks.com/help/matlab/ref/times.html

Also very important to read and understand:

https://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html

@Dyuman Joshi: it is true. Note however that Mathieu NOE has confused DOT with TIMES.

[Walter Roberson]

MATLAB does not have any dot operator. MATLAB has a series of operators whos representation involves two characters, the first of which happens to be a dot.

So in A.*B that is not parsed as A followed by an operator '.' followed by an operator '*' followed by B: it is parsed as A followed by a single operator designated by '.*' followed by B.

This is similar to the way that A>=B is not parsed as A followed by a > operator then a = operator then B, but is instead A followed by a single operator designed by '>=' followed by B

[chaaru datta]

Thank you so much to all of you for your responses...