Creating a function with variable number of inputs?

Question

I am trying to define the following function in MATLAB:

file = @(var1,var2,var3,var4) ['var1=' num2str(var1) 'var2=' num2str(var2) 'var3=' num2str(var3) 'var4=' num2str(var4)'];

However, I want the function to expand as I add more parameters; if I wanted to add the variable vark, I want the function to be:

file = @(var1,var2,var3,var4,vark) ['var1=' num2str(var1) 'var2=' num2str(var2) 'var3=' num2str(var3) 'var4=' num2str(var4) 'vark=' num2str(vark)'];

Is there a systematic way to do this?

You don't intend to use the outputs with eval later, right...? — Dev-iL
– Dev-iL, Commented Oct 7, 2016 at 7:02
Please consider accepting one of the answers if they solved your problem. It's the check mark on the left side of the answer. Thanks! :) — Stewie Griffin
– Stewie Griffin, Commented Oct 14, 2016 at 11:35

Stewie Griffin · Accepted Answer · 2016-10-07 07:08:36Z

Use fprintf with varargin for this:

f = @(varargin) fprintf('var%i= %i\n', [(1:numel(varargin));[varargin{:}]])
f(5,6,7,88)
var1= 5
var2= 6
var3= 7
var4= 88

The format I've used is: 'var%i= %i\n'. This means it will first write var then %i says it should input an integer. Thereafter it should write = followed by a new number: %i and a newline \n.

It will choose the integer in odd positions for var%i and integers in the even positions for the actual number. Since the linear index in MATLAB goes column for column we place the vector [1 2 3 4 5 ...] on top, and the content of the variable in the second row.

By the way: If you actually want it on the format you specified in the question, skip the \n:

f = @(varargin) fprintf('var%i= %i', [(1:numel(varargin));[varargin{:}]])

f(6,12,3,15,5553)
var1= 6var2= 12var3= 3var4= 15var5= 5553

Also, you can change the second %i to floats (%f), doubles (%d) etc.

If you want to use actual variable names var1, var2, var3, ... in your input then I can only say one thing: Don't! It's a horrible idea. Use cells, structs, or anything else than numbered variable names.

Just to be crytsal clear: Don't use the output from this in MATLAB in combination with eval! eval is evil. The Mathworks actually warns you about this in the official documentation!

Priyom · Accepted Answer · 2016-10-07 06:09:57Z

0

How about calling the function as many times as the number of parameters? I wrote this considering the specific form of the character string returned by your function where k is assumed to be the index of the 'kth' variable to be entered. Array var can be the list of your numeric parameters.

file=@(var,i)[strcat('var',num2str(i),'=') num2str(var) ];

var=[2,3,4,5];

str='';

for i=1:length(var);

str=strcat(str,file(var(i),i));

end

answered Oct 7, 2016 at 6:09

Priyom

12 bronze badges

Comments

Erfan · Accepted Answer · 2016-10-07 07:21:13Z

0

If you want a function to accept a flexible number of input arguments, you need varargin.

In case you want the final string to be composed of the names of your variables as in your workspace, I found no way, since you need varargin and then it looks impossible. But if you are fine with having var1, var2 in your string, you can define this function and then use it:

function str = strgen(varargin)
str = '';
for ii = 1:numel(varargin);
    str = sprintf('%s var%d = %s', str, ii, num2str(varargin{ii}));
end
str = str(2:end); % to remove the initial blank space

It is also compatible with strings. Testing it:

% A = pi;
% B = 'Hello!';

strgen(A, B)

ans =

var1 = 3.1416 var2 = Hello!

edited Oct 7, 2016 at 7:21

answered Oct 7, 2016 at 6:09

Erfan

1,92715 silver badges25 bronze badges

Collectives™ on Stack Overflow

Creating a function with variable number of inputs?

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related