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Sometimes the number of input arguments is not known when the function is defined. As an example think of a function that returns the smallest of all its input arguments. For example:
a = smallest (1, 2, 3); b = smallest (1, 2, 3, 4);
In this example both a
and b
would be 1. One way to write
the smallest
function is
function val = smallest (arg1, arg2, arg3, arg4, arg5) body endfunction
and then use the value of nargin
to determine which of the input
arguments should be considered. The problem with this approach is
that it can only handle a limited number of input arguments.
If the special parameter name varargin
appears at the end of a
function parameter list it indicates that the function takes a variable
number of input arguments. Using varargin
the function
looks like this
function val = smallest (varargin) body endfunction
In the function body the input arguments can be accessed through the
variable varargin
. This variable is a cell array containing
all the input arguments. See Cell Arrays, for details on working
with cell arrays. The smallest
function can now be defined
like this
function val = smallest (varargin) val = min ([varargin{:}]); endfunction
This implementation handles any number of input arguments, but it’s also a very simple solution to the problem.
A slightly more complex example of varargin
is a function
print_arguments
that prints all input arguments. Such a function
can be defined like this
function print_arguments (varargin) for i = 1:length (varargin) printf ("Input argument %d: ", i); disp (varargin{i}); endfor endfunction
This function produces output like this
print_arguments (1, "two", 3); -| Input argument 1: 1 -| Input argument 2: two -| Input argument 3: 3
Return in reg the cell elements of param up to the first string element and in prop all remaining elements beginning with the first string element.
For example:
[reg, prop] = parseparams ({1, 2, "linewidth", 10}) reg = { [1,1] = 1 [1,2] = 2 } prop = { [1,1] = linewidth [1,2] = 10 }
The parseparams function may be used to separate regular numeric arguments from additional arguments given as property/value pairs of the varargin cell array.
In the second form of the call, available options are specified directly with their default values given as name-value pairs. If params do not form name-value pairs, or if an option occurs that does not match any of the available options, an error occurs.
When called from an m-file function, the error is prefixed with the name of the caller function.
The matching of options is case-insensitive.
See also: varargin, inputParser.
Next: Ignoring Arguments, Previous: Variable-length Return Lists, Up: Functions and Scripts [Contents][Index]