narginchk and varargin in MATLAB

Question

DM 2015-4-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/211363-narginchk-and-varargin-in-matlab

评论： Walter Roberson 2023-4-20

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

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Answer 1

James Tursa 2015-4-20

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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.

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Answer 2

Lei 2023-4-20

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/211363-narginchk-and-varargin-in-matlab#answer_1219438

编辑：Walter Roberson 2023-4-20

在 MATLAB Online 中打开

Recode

function p= marie (p,q)
narginchk[2,3]
disp('Yo, G!')
a=p+q
end

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Walter Roberson 2023-4-20

在 MATLAB Online 中打开

%if the user passes in no parameters then none of the parameters will exist
%if the user passes in too few parameters then variable p will not exist
%if the user passes in more than 3 parameters then there will be a 4th
%parameter and that should be rejected
%
%note that we are accepting a third parameter even though we do not do
%anything with it. This is because the original code permitted either 2 or
%3 inputs.
function p = marie (p,q,extra_ok,extra_not_ok)
    if ~exist(p, 'var') || exist('extra_not_ok', 'var')
        error('You must pass in either 2 or 3 inputs')
    end
    disp('Yo, G!')
    a=p+q
end