varargin

Variable-length input argument list

Syntax

varargin

Description

varargin is an input variable in a function definition statement that enables the function to accept any number of input arguments. Specify varargin using lowercase characters, and include it as the last input argument after any explicitly declared inputs.

When the function executes, varargin is a 1-by-N cell array, where N is the number of inputs that the function receives after the explicitly declared inputs. However, if the function receives no inputs after the explicitly declared inputs, then varargin is an empty cell array.

Examples

Variable Number of Function Inputs

Define a function in a file named acceptVariableNumInputs.m that accepts a variable number of inputs and displays the values of each input.

type acceptVariableNumInputs

function acceptVariableNumInputs(varargin)
    disp("Number of input arguments: " + nargin)
    celldisp(varargin)
end

Call the function with several inputs.

acceptVariableNumInputs(ones(3),'some text',pi)

Number of input arguments: 3
 
varargin{1} =
 
     1     1     1
     1     1     1
     1     1     1

 
 
varargin{2} =
 
some text
 
 
varargin{3} =
 
    3.1416

 

varargin and Declared Inputs

Define a function in a file named definedAndVariableNumInputs.m that expects two inputs and accepts an additional number of inputs.

type definedAndVariableNumInputs

function definedAndVariableNumInputs(X,Y,varargin)
    disp("Total number of input arguments: " + nargin)
    
    formatSpec = "Size of varargin cell array: %dx%d";
    str = compose(formatSpec,size(varargin));
    disp(str)

end

Call the function with several inputs.

definedAndVariableNumInputs(7,pi,rand(4),datetime('now'),'hello')

Total number of input arguments: 5
Size of varargin cell array: 1x3

Call the function with two inputs. varargin is an empty cell array.

definedAndVariableNumInputs(13,42)

Total number of input arguments: 2
Size of varargin cell array: 0x0

Variable Number of Inputs and Outputs

Define a function in a file named variableNumInputAndOutput.m that accepts a variable number of inputs and outputs.

type variableNumInputAndOutput

function varargout = variableNumInputAndOutput(varargin)
    disp(['Number of provided inputs: ' num2str(length(varargin))])
    disp(['Number of requested outputs: ' num2str(nargout)])
    
    for k = 1:nargout
        varargout{k} = k;
    end
end

Call the function with two inputs and three outputs.

[d,g,p] = variableNumInputAndOutput(6,'Nexus')

Number of provided inputs: 2
Number of requested outputs: 3

d = 1

g = 2

p = 3

Call the function again with no inputs or outputs.

variableNumInputAndOutput

Number of provided inputs: 0
Number of requested outputs: 0

Create Function Wrapper

In a file in your working folder, create a wrapper to the plot function that plots a red line. The redplot function accepts a variable-length input argument list and returns a variable-length output argument list. It sets the line color to red, and forwards other input values to the plot function. This function wrapper enables you to pass redplot the same inputs as plot and not specify that the line color is red.

type redplot.m

function varargout = redplot(varargin)
    [varargout{1:nargout}] = plot(varargin{:},'Color',[1,0,0]);
end

Use redplot to create a line plot.

x = 0:pi/100:2*pi;
y = sin(x);
redplot(x,y)

Call redplot again, and specify input and output arguments to forward to the plot function.

h = redplot(x,y,'Marker','o','MarkerEdgeColor','green'); 

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

• If you use varargin to define an argument to an entry-point (top-level) function, the code generator produces a C/C++ function with a fixed number of input arguments. The number of arguments that you specify when you generate code determines the fixed number of arguments.

• You cannot write to varargin. If you want to write to input arguments, first copy the input arguments into a local variable.

• The index into varargin must be a compile-time constant.