What does mean .* and ' ?

Hi,

It seems that in MATLAB exists the notation .* that seems to be an operation and the notation ' that is used apparently with variables.

What is the meaning of these notations?

Answer 1

[Steven Lord]

The .* operator performs element-wise multiplication.

The ' character has at least three potential meanings that I can think of offhand.

The first potential meaning is that of the complex conjugate transpose.

A = [1 2+3i; 4 5+5i]
B = A'

Note that each row in B contains the same values as the corresponding column of A, except that complex numbers are replaced with their complex conjugates.

The second potential meaning is to create a char vector. This could be what Sara Boznik meant with "you use it usually when you want to have something displayed in Command Window."

x = 'apple'

The third is relevant inside a char vector. Two ' characters will create a single ' stored inside the char vector.

y = 'Simple, isn''t it?'

Answer 2

[Sara Boznik]

.* means matrix product, if you don't write . will Matlab product the numbers on the same position.

' you use it usually when you want to have something displayed in Command Window.

Good luck.

[Stephen23]

".* means matrix product, if you don't write . will Matlab product the numbers on the same position."

This is incorrect. In fact:

• * is matrix multiplication,
• .* is array multiplication (i.e. element-wise).

The difference is explained here:

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

"' you use it usually when you want to have something displayed in Command Window."

The complex conjugate transpose should be used when you need the complex conjugate transpose.

Answer 3

[KSSV]

.* this mean element by element multiplication. https://www.mathworks.com/help/matlab/ref/times.html

Example:

A = [1 2 ; 3 4] ;
B = [5 6 ; 7 8] ;
C = A.*B 

' this stands for transpose of a matrix. https://www.mathworks.com/help/matlab/ref/transpose.html

EXample:

A = [1 2 ; 3 4] ;
B = A'

[Stephen23]

"' this stands for transpose of a matrix. https://www.mathworks.com/help/matlab/ref/transpose.html "

This is incorrect. In fact

• ' is shorthand for complex conjugate transpose.
• .' is shorthand for transpose.

Sadly beginners often confuse the two, although they are not the same operation.