GNU Octave Manual Version 3by John W. Eaton, David Bateman, Søren Hauberg Paperback (6"x9"), 568 pages ISBN 095461206X RRP £24.95 ($39.95) |

## 11.2 Multiple Return Values

Unlike many other computer languages, Octave allows you to define functions that return more than one value. The syntax for defining functions that return multiple values is

function [ret-list] =name(arg-list)bodyendfunction

where `name`, `arg-list`, and `body` have the same meaning
as before, and `ret-list` is a comma-separated list of variable
names that will hold the values returned from the function. The list of
return values must have at least one element. If `ret-list` has
only one element, this form of the `function`

statement is
equivalent to the form described in the previous section.

Here is an example of a function that returns two values, the maximum element of a vector and the index of its first occurrence in the vector.

function [max, idx] = vmax (v) idx = 1; max = v (idx); for i = 2:length (v) if (v (i) > max) max = v (i); idx = i; endif endfor endfunction

In this particular case, the two values could have been returned as elements of a single array, but that is not always possible or convenient. The values to be returned may not have compatible dimensions, and it is often desirable to give the individual return values distinct names.

In addition to setting `nargin`

each time a function is called,
Octave also automatically initializes `nargout`

to the number of
values that are expected to be returned. This allows you to write
functions that behave differently depending on the number of values that
the user of the function has requested. The implicit assignment to the
built-in variable `ans`

does not figure in the count of output
arguments, so the value of `nargout`

may be zero.

The `svd`

and `lu`

functions are examples of built-in
functions that behave differently depending on the value of
`nargout`

.

It is possible to write functions that only set some return values. For example, calling the function

function [x, y, z] = f () x = 1; z = 2; endfunction

as

[a, b, c] = f ()

produces:

a = 1 b = [](0x0) c = 2

along with a warning.

__Built-in Function:__**nargout***()*__Built-in Function:__**nargout***(*`fcn_name`)- Within a function, return the number of values the caller expects to
receive. If called with the optional argument
`fcn_name`, return the maximum number of values the named function can produce, or -1 if the function can produce a variable number of values.For example,

f ()

will cause

`nargout`

to return 0 inside the function`f`

and[s, t] = f ()

will cause

`nargout`

to return 2 inside the function`f`

.At the top level,

`nargout`

is undefined.See also nargin, varargin, varargout

__Function File:__**nargchk***(*`nargin_min`,`nargin_max`,`n`)- If
`n`is in the range`nargin_min`through`nargin_max`inclusive, return the empty matrix. Otherwise, return a message indicating whether`n`is too large or too small.This is useful for checking to see that the number of arguments supplied to a function is within an acceptable range.

ISBN 095461206X | GNU Octave Manual Version 3 | See the print edition |