subset of varargin as function input

I call a function in the main code

plotFT( var1,var2,...,var13)

whose input variable can be either 10 or 13. The function in subject is defined as follows:

function plotFT( varargin )
      switch nargin
            case 10
                fun1( varargin{1:10} ) %why doesn't work just with varargin as input?
            case 13
                subplot(1,2,1)
                fun1( varargin{1:10} )
                subplot(1,2,2)
                fun2( [ varargin{1:3} varargin{11:13} ] );  %I can't't catch the mistake    
            otherwise 
                warning('Unexpected number of inputs')
        end

fun1 works but for fun2 the followinf error message is prompted: "Error using horzcat. The following error occurred converting from char to struct: Conversion to struct from char is not possible." Questin1:

Answer 1

[Stephen23]

Try this:

function plotFT(varargin)
switch nargin
    case 10
        fun1(varargin{:})    
    case 13
        subplot(1,2,1)
        fun1(varargin{1:10})
        subplot(1,2,2)
        fun2(varargin{[1:3,11:13]});
    otherwise
        warning('Unexpected number of inputs')
end

"why doesn't work just with varargin as input?"

Because varargin is one cell array. If fun1 expects ten separate inputs, then you cannot just pass it one cell array. The syntax cellarray{...} generates a comma-separated list, which is equivalent to writing each cell as its own input argument, like this:

 fun1(varargin{1}, varargin{2}, ... )

To learn more about comma-separated lists read this explanation:

https://www.mathworks.com/matlabcentral/answers/320713-how-to-operate-on-comma-separated-lists

"I can't't catch the mistake"

Because you try to concatenate the contents of varargin together, which clearly does not make sense for your input arrays, because they are different classes/sizes/...

After reading the links I gave you, you will know that your code

[ varargin{1:3} varargin{11:13} ]

is exactly equivalent to this

[varargin{1},varargin{2},varargin{3},varargin{11},varargin{12},varargin{13}]

Is there much point in concatenating all of them together? I doubt it. Most likely you want them as separate inputs, which, after reading the links I gave you, you will know that you can achieve using either of these two syntaxes:

fun2(varargin{[1:3,11:13]})
fun2(varargin{1:3},varargin{11:13})

both of which are equivalent to writing

fun2(varargin{1},varargin{2},varargin{3},varargin{11},varargin{12},varargin{13})

which I suspect is what you were trying to achieve (although you do not actually specify anything about fun2 in your question, such as how many inputs it requires, so I had to guess).

[Steven Lord]

As a side note to Stephen's correct answer, if your function requires ten or thirteen input arguments, I would explore passing them in as a struct array or using parameter name/value pairs instead of requiring them to be passed in using a specific order.

If you require them to be passed in positionally, the odds are pretty good that a user of your code is going to accidentally omit one or pass them in using a different order and (hopefully) receive an error message that clearly indicates the problem.

The error message you receive if you try to reference a field of a struct array passed into your function as input should be easier to understand. If you use parameter name/value pairs, you can use inputParser to parse those inputs and throw an error if one of the inputs the user was require to specify was missing.

[Luigi]

Thanks for the answer. The two functions have been defined as follows:

fun1( var1,var2,...,var10 )  
...
end
fun2( var1,var2,var3,var11,var12,var13 )
...
end

so the function fun2 is called only if nargin = 13 in plotFT. So the problem is that I have defined the input of the functions fun1 and fun2 as separate variables and then I have to specify the number of input input variable, is it right? Is that a good practice? Or could/should I define the input of fun1 and fun2 as a vector (?), e.g.

fun2( var_vett )
var1 = var_vett(1);
var2 = var_vett(2): %and so on
...
end

[Stephen23]

@drSlump: do whatever is clearest for your code. A structure, as Steven Lord suggested, might be a good idea. Ten inputs might be okay. I don't think using one vector would be an improvement, as having individual inputs/structure fields makes the purpose, documentation, and checking clear, if a little verbose. Using one cell array requires processing of the cell array to check/count/.. its contents.