what is the matlab .' (dot-quote) notation?

Question

Trying to understand MATLAB syntax: I see that

(0:3)

is a row vector, that the ' (forward-quote) operator is transpose, so

(0:3)'

is a column vector. I have also seen .' in some files, and these also produce column vectors, so

(0:3).'

produces the same result as (0:3).

What is the difference between ' and .'? I haven't found anything in the MATLAB docs to help me understand this.

(note that this question is about syntax, primarily, not about the difference between transpose and ctranspose, because if you don't know that ' is one and .' is the other, than an answer to the question of transpose versus ctranspose is of no help answering the question of . versus '.. In many MATLAB examples and tutorials, ' is glibly and inaccurately presented as transpose, and that fact leads to the question when a user first encounters .'.)

Quintessence: Always use `.'` and get used to it, unless you really know what you're doing and you really need `'`. — Robert Seifert, Apr 07 '15 at 16:52

Andrey Rubshtein · Accepted Answer · 2015-04-07T16:43:10.017

11

There is no difference for real numbers. For complex numbers .' will produce transpose, while ' will produce the complex conjugate.

>> [i -i].'

ans =

   0.0000 + 1.0000i
   0.0000 - 1.0000i

>> [i -i]'

ans =

   0.0000 - 1.0000i
   0.0000 + 1.0000i

By the way, each Matlab operator has a name, which can be used to read the documentation.

.' - transpose
' - ctranspose

Though it is hard to find them in the documentation sometimes. Most of them can be found in here, but you will have to guess which operator is which.

edited Apr 07 '15 at 16:43

answered Apr 07 '15 at 16:18

Andrey Rubshtein

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It would be brilliant if you found a Matlab resource that explains that `.'` is transpose and `'` is ctranspose. – kkuilla Apr 07 '15 at 16:38
@kkuilla, I agree. Still looking for it – Andrey Rubshtein Apr 07 '15 at 16:44
4

@kkuilla Type `help punct`. Quoting: _X' is the complex conjugate transpose of X. X.' is the non-conjugate transpose._ BTW, congrats on your 1k rep! – Luis Mendo Apr 07 '15 at 16:45
@LuisMendo, thanks that looks good. But it does not cover function like `gt`,`lt`. – Andrey Rubshtein Apr 07 '15 at 16:46
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@Andrey That's `help relop` – Luis Mendo Apr 07 '15 at 16:46
@LuisMendo, cool! How about `+`? Maybe you could compile all of them into an answer? Maybe even starting a new question? That would be extremely helpful – Andrey Rubshtein Apr 07 '15 at 16:47
@Andrey I think `+` does not belong to any general category: just `help plus`, `help minus`, `help times` etc. Your suggestion sounds like a good idea, but I doubt what the question to that answer would be, or if it would be really useful – Luis Mendo Apr 07 '15 at 16:49
3

@Andrey Oh, there is such category: `help arith` – Luis Mendo Apr 07 '15 at 16:50
@LuisMendo Thank you. A milestone for me... :) – kkuilla Apr 08 '15 at 07:57

what is the matlab .' (dot-quote) notation?

1 Answers1