varargin

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Ahmed Tawfeeq
Ahmed Tawfeeq 2012-2-14
编辑： sixwwwwww 2013-10-12
what is varargin used for ?and how to use it? and can I change it to an ordinary input variable?

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Walter Roberson
Walter Roberson 2012-2-14
http://www.mathworks.com/help/techdoc/ref/varargin.html
There are situations in which it is not possible to use any fixed number of arguments, so conversion depends upon what your code does.

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Matt Tearle
Matt Tearle 2012-2-14
It is used for situations where you want to allow any number of input arguments (so you can't list them). A common reason for that is optional settings -- in MATLAB this is often done with property name/property value pairs. For example, think of how you can pass extra options to plot:
plot(x,y) % plain
plot(x,y,'LineWidth',4)
plot(x,y,'Marker','o','LineWidth',2)
plot(x,y,'Marker','o','LineWidth',2,'MarkerFaceColor','r')
etc. Here you don't want to force the user to input all the possible optional parameters in a specific order, so instead you allow them to specify 'MagicPropertyName' takes the value PropertyValue (eg 'LineWidth' takes the value 2).
To write a function that can do this, you'd make a function declaration like
function plot(x,y,varargin)
Then inside this function, x takes the value of the first input, y takes the value of the second, and all the rest go into cells of the cell array varargin. So, in the last example, varargin would be a 1-by-6 cell array; varargin{1} would be the string 'Marker', varargin{4} would be the number 2, etc.
So obviously there's a bunch of programming you have to do as the developer to parse the elements of varargin, and make your code behave accordingly.
I don't really understand the last question. Could you elaborate?
(Note: the actual plot function is actually even more flexible than this -- the above function declaration line is for illustration only.)
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Walter Roberson
Walter Roberson 2012-2-14
You cannot pass adaptfilt.lms objects around in Simulink . No efforts along the line of calling lms.m directly are going to work.
Walter Roberson
Walter Roberson 2012-2-14
Alternatives discussed in one of your other Questions.

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Benjamin Schwabe
Benjamin Schwabe 2012-2-14
varargin is used when the number of input parameter might change. Basically, it puts all input arguments into a cell array. The number of input parameters is given by
nargin.
You can access any of the input values inside the function by
varargin{ind}
where ind is the index number of your argument.

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