What the difference between using bracket and not.

Hi I'm newbie of matlab.

function varargout = redplot(varargin)
    [varargout{1:nargout}] = plot(varargin{:},'Color',[1,0,0]);
end

this code doesn't appear the error.

but

function varargout = redplot(varargin)
    varargout{1:nargout} = plot(varargin{:},'Color',[1,0,0]);
end

this code shows the error.

i don't know why the last cod appears the error.

the difference between them is [ ].

what is the role [ ] in this code.

Thank you.

Answer 1

[Stephen23]

None of the answers explain why this works, nor even mentioned the useful-to-know name of this syntax.

The actual reason is because that syntax combines two different syntaxes together. These are:

1- multiple function outputs are always indicated by square brackets, the outputs are written in the form of a comma-separated list, e.g.:

[a,b,c,d] = somefun();

This is explained in the introductory tutorials:

https://www.mathworks.com/help/matlab/learn_matlab/calling-functions.html

2- one cell array can be converted to (or from) a comma-separated list using this syntax:

somecell{:}

which is equivalent to this comma-separated list:

somecell{1},somecell{2},somecell{3},...

Read more about how comma-separated lists work:

https://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html

https://www.mathworks.com/matlabcentral/answers/1656435-tutorial-comma-separated-lists-and-how-to-use-them

Combine these two different syntaxes into one, to allocate multiple function outputs into one cell array:

[somecell{:}] = somefun();

Add indexing as required.

PS: the syntax somecell{:}=somefun() is meaningless.

Answer 2

[Fangjun Jiang]

I think the fundenmental reason is that the function definition requires that the left side contains "[ ]" when there are multiple outputs. See "doc function".

[Junu Lee]

thanks a lot Fangjun!