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Variable-length output argument list




varargout is an output variable in a function definition statement that enables the function to return any number of output arguments. Specify varargout using lowercase characters, and include it as the last output argument after any explicitly declared outputs.

When the function executes, varargout is a 1-by-N cell array, where N is the number of outputs requested after the explicitly declared outputs. Inside of a function, varargout is an uninitialized variable and is not preallocated.


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Define a function in a file named returnVariableNumOutputs.m that returns an output size vector s and a variable number of additional outputs.

type returnVariableNumOutputs
function [s,varargout] = returnVariableNumOutputs(x)
    nout = max(nargout,1) - 1;
    s = size(x);
    for k = 1:nout
        varargout{k} = s(k);

Output s contains the dimensions of the input array x. Additional outputs correspond to the individual dimensions within s.

Call the function with a three-dimensional array and request three outputs.

A = rand(4,5,2);
[s,rows,cols] = returnVariableNumOutputs(A)
s = 1×3

     4     5     2

rows = 4
cols = 5

Call the function again with a four-dimensional array and request four outputs. This time, the function does not return the individual fourth dimension.

A = zeros(1,4,5,2);
[s,dim1,dim2,dim3] = returnVariableNumOutputs(A)
s = 1×4

     1     4     5     2

dim1 = 1
dim2 = 4
dim3 = 5

Call the function once more on A and request one output. Now the function returns the dimensions of A and not varargout.

s = returnVariableNumOutputs(A)
s = 1×4

     1     4     5     2

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;

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.

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

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]);

Use redplot to create a line plot.

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

Figure contains an axes. The axes contains an object of type line.

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

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

Figure contains an axes. The axes contains an object of type line.

Extended Capabilities

Introduced before R2006a