narginchk and varargin in MATLAB

I have come across PART of a code in MATLAB in a toolbox that I don't understand

    elseif (txMode==2) 

    narginchk(7, 7);
    numTx = varargin{1};
    numRx = varargin{2};

    switch numTx
        case 2    
            numCSRRE_RB = 4*2*2; 
        case 4      
            numCSRRE_RB = 4*3*2; 
    end

I don't understand what `narginchk` and `varargin` are used for in this example, and why is that the output of `varargin{1}` would be either 2 or 4 (a conclusion I came up with when looking at the code after `switch`).

Thanks

Answer 1

[James Tursa]

narginchk(7, 7) throws an error if the number of input arguments is less than 7 or greater than 7 (i.e., the number of input arguments must be exactly 7 in this case or an error will be thrown).

varargin{1} is the first input argument.

varargin{2} is the second input argument.

Why the value of varargin{1} should be 2 or 4 would depend on the code in question and how it is called.