There is still one additional problem with this function. What if it is called without an argument? To allow you to catch errors like this, Octave provides each function with an automatic variable called nargin.
Each time a function is called, nargin is automatically initialized to the number of arguments that have actually been passed to the function. For example, we might rewrite the avg function like this:. Although Octave does not automatically report an error if you call a function with more arguments than expected, doing so probably indicates that something is wrong.
Octave also does not automatically report an error if a function is called with too few arguments, but any attempt to use a variable that has not been given a value will result in an error. To avoid such problems and to provide useful messages, we check for both possibilities and issue our own error message. Called from within a function, return the number of arguments passed to the function. At the top level, return the number of command line arguments passed to Octave.
If called with the optional argument fcn —a function name or handle—return the declared number of arguments that the function can accept. If the last argument to fcn is varargin the returned value is negative. For example, the function union for sets is declared as. Programming Note: nargin does not work on compiled functions. We recommend the Octave installer for Windows, which has all toolboxes signal processing, statistics, etc… pre-installed.
If you are running Octave on Linux or macOS, in addition to Octave, you will need to install the Octave signal processing and statistics package. On the Octave command line, type:. If the package is installed successfully nothing will be printed on the prompt, but if an error occurred during installation it will be reported. It is possible to install several packages at once by writing several package files after the pkg install command.
If a different version of the package is already installed it will be removed prior to installing the new package. This makes it easy to upgrade and downgrade the version of a package, but makes it impossible to have several versions of the same package installed at once. In this case only version 1. It is possible to remove a package from the system using the pkg uninstall command like this. If the package is removed successfully nothing will be printed in the prompt, but if an error occurred it will be reported.
It should be noted that the package file used for installation is not needed for removal, and that only the package name as reported by pkg list should be used when removing a package. It is possible to remove several packages at once by writing several package names after the pkg uninstall command.
To minimize the amount of code duplication between packages it is possible that one package depends on another one. If a package depends on another, it will check if that package is installed during installation.
If it is not, an error will be reported and the package will not be installed. This behavior can be disabled by passing the -nodeps flag to the pkg install command. Since the installed package expects its dependencies to be installed it may not function correctly.
Because of this it is not recommended to disable dependency checking. Different actions are available depending on the value of command and on return arguments. The file containing the package can be an url, e. This requires an internet connection and the cURL library. Security risk : no verification of the package is performed before the installation. It has the same security issues as manually downloading the package from the given url and installing it.
No support : the GNU Octave community is not responsible for packages installed from foreign sites.
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