nargin，vargin，存在，什么是实现可选参数的最佳方法matlab [英] nargin, vargin, exist, what is the best way to implement optional arguments matlab

问题描述

我在matlab中有一个功能:

I have a function in matlab:

function output = myfunc(a,b,c,d,e)
      %a and b are mandetory
      %c d and e are optional
end 

如果用户给e而不是c和d给出了可选的arg，我将如何处理输入?

How would I handle inputs if a user gave an optional arg for e but not for c and d?

nargin仅给出参数的数量.会是最好的方法吗?

nargin just gives the number of arguments. would exist be the best way?

推荐答案

只需使用 nargin .它会告诉您有多少参数.仅当具有变量个参数时，即您对参数的数量没有限制，或者您希望以索引方式访问这些参数时，才使用varargin.我认为情况并非如此，因此一种解决方案可能看起来像这样.

Just use nargin. It will tell you how many arguments are present. Use varargin only when you have a variable number of arguments, that is you have no limit in number of arguments, or you want to access the arguments in an indexing fashion. I assume this is not the case for you, so one solution might look like this.

function output = myfunc(a,b,c,d,e)
  %a and b are mandetory
  %c d and e are optional
  if nargin < 3 || isempty(c)
     c = <default value for c>
  end
  if nargin < 4 || isempty(d)
     d = <default value for d>
  end
  if nargin < 5 || isempty(e)
     e = <default value for e>
  end
  <now do dome calculation using a to e>
  <If a or b is accessed here, but not provded by the caller an error is generated by MATLAB>

如果用户不想为c或d提供值，而是提供e，则必须通过[]，例如 func(a，b，c，[]，e)，以省略d.

If the user does not want to provide a value for c or d but provides e, he has to pass [], e.g. func(a,b,c,[],e), to omit d.

或者，您可以使用

if nargin == 5
   <use a b c d and e>
elseif nargin == 2
   <use a and b>
else    
   error('two or five arguments required');
end

检查是否存在所有参数e.但这恰好需要2或5个参数.

to check if all a arguments e are present. But this requires exactly 2 or 5 arguments.

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