how to use nargin function to take variable input arguments and return sum of those arguments

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KayLynn 2013-10-26

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编辑： Cedric 2013-10-27

I am not sure how to use the nargin function. I wanted to take a variable number of input arguments and return a sum of those arguments. I am stuck. I have this code so far

function [ output_args ] = addmany() %This function will take zero or more numbers as a variable number of input %arguments and returns the sum of its input arguments. n=nargin; %number of input arguments sum

Not sure how to get a sum of the variable input arguments

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Jan 2013-10-26

Start with 2 inputs at first to get some experiences with the addition.

Cedric 2013-10-26

See my answer.

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Answer 1

Cedric 2013-10-26

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编辑：Cedric 2013-10-26

在 MATLAB Online 中打开

Well, if you had a function

 function x = doSomething(a, b, c, d)
    ...
 end

nargin would tell you how many input arguments were present at the call, which would allow you e.g. to define default values for c and d if nargin were equal to 2. Now as you can see, this function has only 4 named input parameters, so this approach is not that well suited for a function which should accept any number of arguments.. what if a user calls your function with 500 arguments, are you going to define 500 named parameters just to be sure?

What we usually do is to use varargin, as follows

 function x = doSomething(varargin)
    ...
 end

In that case, varargin is a cell array inside the function, which contains all the arguments from the call.

Now as it's a homework, I cannot write the full code for you, but this hints sets you on a better track already. The next step should be to understand how to deal with cell arrays so you can compute a sum.

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Cedric 2013-10-27

编辑：Cedric 2013-10-27

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As Matt is pointing out, concatenating varargin developed as a Comma Separated List is probably the way we would get the content of varargin. If this looks too complicated to you, you could use CELL2MAT.. execute the following in the command window to understand how:

doc cell2mat

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Answer 2

Matt J 2013-10-26

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编辑：Matt J 2013-10-26

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it is a statement of homework but there is no specifics as to what commands are able to be used

If there are no restrictions, the better solution would be not to use separate arguments at all. Just put all arguments in a vector x and do sum(x).

 function y = addmany(x) 
    y=sum(x);
 end
>> y=addmany([1 2 3 4])
y =
      10

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KayLynn 2013-10-26

I am trying to add a variable number of input arguments....Doesnt addmany(x) only add one of the inputs. Lets say I was trying to input ten varaibles ( just picking a random number), How would I be able to do so...Do i have to list each of the variable inputs or is there something I can do to take any variable number of inputs and find the sum of them

Matt J 2013-10-27

编辑：Matt J 2013-10-27

Doesnt addmany(x) only add one of the inputs.

Yes, but it's not clear why the summands have to be passed as separate input arguments rather than as elements of one single vector. Was that a requirement of the homework assignment?

or is there something I can do to take any variable number of inputs and find the sum of them

Yes, there is a way, and Cedric gave you strong hints. Here is another small one

http://www.mathworks.com/help/matlab/matlab_prog/comma-separated-lists.html;jsessionid=7520a0f866264cbdf6af2d301187?s_tid=doc_12b#br2js35-12

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