help (MATLAB Function Reference)

help	Examples See Also

Online help for MATLAB functions and M-files

Syntax

help
help topic

Description

help,

by itself, lists all primary help topics. Each main help topic corresponds to a directory name on MATLAB's search path.

help topic

gives help on the specified topic. The topic can be a function name, a directory name, or a MATLABPATH relative partial pathname If it is a function name, help displays information on that function. If it is a directory name, help displays the contents file for the specified directory. It is not necessary to give the full pathname of the directory; the last component, or the last several components, is sufficient.

It's possible to write help text for your own M-files and toolboxes; see Remarks.

Remarks

MATLAB's Help system, like MATLAB itself, is highly extensible. This allows you to write help descriptions for your own M-files and toolboxes - using the same self-documenting method that MATLAB's M-files and toolboxes use.

The command help, by itself, lists all help topics by displaying the first line (the H1 line) of the contents files in each directory on MATLAB's search path. The contents files are the M-files named Contents.m within each directory.

The command help topic, where topic is a directory name, displays the comment lines in the Contents.m file located in that directory. If a contents file does not exist, help displays the H1 lines of all the files in the directory.

The command help topic, where topic is a function name, displays help on the function by listing the first contiguous comment lines in the M-file topic.m.

Creating Online Help for Your Own M-Files

Create self-documenting online help for your own M-files by entering text on one or more contiguous comment lines, beginning with the second line of the file (first line if it is a script). (See Applying MATLAB for information about creating M-files.) For example, an abridged version of the M-file angle.m provided with MATLAB could contain:

function p = angle(h)
% ANGLE Polar angle.
% ANGLE(H) returns the phase angles, in radians, of a matrix
% with complex elements. Use ABS for the magnitudes.
p = atan2(imag(h),real(h));

When you execute help angle, lines 2, 3, and 4 display. These lines are the first block of contiguous comment lines. The help system ignores comment lines that appear later in an M-file, after any executable statements, or after a blank line.

The first comment line in any M-file (the H1 line) is special. It should contain the function name and a brief description of the function. The lookfor command searches and displays this line, and help displays these lines in directories that do not contain a Contents.m file.

Creating Contents Files for Your Own M-File Directories

A Contents.m file is provided for each M-file directory included with the MATLAB software. If you create directories in which to store your own M-files, you should create Contents.m files for them too. To do so, simply follow the format used in an existing Contents.m file.

Examples

The command

help datafun

gives help on the datafun directory.

To prevent long descriptions from scrolling off the screen before you have time to read them, enter more on; then enter the help command.