Looking for documentation explaining M.' and other symbols to select data from an array

I have seen the use of this for getting a row from a matrix M.

M. means the same as M(:,:)

I do find documentation on dot notation but still do not understand the use of the last symbol ' here.

Why do you conjugate to find the rows?

And why can I use T=(M.') or T=(M.)' to give me a conjugated matrix and not T=(M.) to give me the matrix itself?

Can somebody please point me to a documentation page where this is explained, where I can find all symbols used to select parts of an array.

Thanks

[Stephen23]

"M. means the same as M(:,:)"

No.

M. is a syntax error.

M(:,:) is not a syntax error, but serves little point for a matrix it just returns M unchanged.

"And why can I use T=(M.') or T=(M.)' to give me a conjugated matrix"

(M.') returns the array transpose, not the complex conjugate transpose. The parentheses are superfluous.

(M.)' is a syntax error.

So neither of them will "give me a conjugated matrix".

Answer 1

[Star Strider]

‘M. means the same as M(:,:)‘

No, not ‘M.’. The extra dot will throw an error.

I am not certain what you are asking. See Special Characters [ ] ( ) {} = ' . ... , ; : % ! @ for a list of them and their explanations.

[Erwin Serlé]

The page you were looking for does not exist. Use the search box or browse topics below to find the page you were looking for.

It is more difficult to ask a correct question than to get helpful answers.

I was trying to find a matrix notation that works with the functions max() and min()

Of and by itself N' N.' N(:)' N(:,:)' are all valid from a syntax perspective. And with or without using the ' to get a Transposes array (indeed).

My conclusion came from that use:

If max(M.') gives me the max value found in each row of M by looking for the max in each column in the transpose of M (wording corrected instead of using the wrong word conjugate) than M. means the whole matrix. But M by itself means the whole matrix. And .' or ' simply deliver the same result.

So thank you for pointing me in the right direction and teaching me the correct use of some difficult words.

[Star Strider]

I did not realise that reference changed.

Try this: MATLAB Operators and Special Characters

‘It is more difficult to ask a correct question than to get helpful answers.’

No worries. It is not always straightforward to put symbolic concepts into words.

Note that max(), min() and most other functions toat have matrix arguments allow the definition of a dimension argument.

For example:

ColMax = max(M, [], 1);                         % Maximum Of Each Column (Default, Dimension 1)
RowMax = max(M, [], 2);                         % Maximum Of Each Row (Dimension 2)
PageMax = max(M, [], 3);                        % Maximum Across ‘Pages’ (Dimension 3)

.

[Stephen23]

"I was trying to find a matrix notation that works with the functions max() and min()"

"If max(M.') gives me the max value found in each row..."

Rather than transposing and then relying on the default behavior of max (which changes what dimension it operates along depending on the size of the input array) you should specify the dimension to operate over as the third input to max:

max(M,[],2)

This will be more efficient and much more robust.

"And .' or ' simply deliver the same result."

For complex matrices they return different results. It is good practice to stick to using transpose .' unless you specifically need a complex conjugate transpose '