MATLAB: Does ‘help matlab’ not give me meaningful information

helpMATLAB

For most of the help topics, the command returns topics in the given toolbox listed as separate subtopics:

For example

>> help fixedpoint 
Contents of fixedpoint: 
NumericTypeScope - Determines fixed-point data type 
aboutfixedpttlbx - Displays version number of the Fixed-Point Designer and 
accumneg - Subtract two fi objects or values 
accumpos - Add two fi objects or values 
accumulatefi - (a,b,mode,...) Undocumented internal function.

If you type 'help matlab' you only get a single line:

>> help matlab 
Contents of matlab: 
DiscreteEventSystem - Copyright 2015 The MathWorks, Inc.

Best Answer

The 'help' command in MATLAB is folder based, and not toolbox based. There isn't a folder on the path called 'matlab' and hence the reason for the output.

An enhancement request to have a more meaningful message printed has been created, so that the development team can consider this for a future release of MATLAB.

Related Solutions

MATLAB: Do I get the error “Undefined ‘matlab.graphics.illustration.internal.getLegendableChildren'” when using the function ‘legend’

This error may be due to the file containing the legend functions not being correctly located. Please check that it can actually be found in the MATLAB path by executing:

>> which -all matlab.graphics.illustration.internal.getLegendableChildren

The output of this command should be something like:

<matlabroot>\toolbox\matlab\graphics\illustration\+matlab\+graphics\+illustration\+internal\getLegendableChildren.m

where 'matlabroot' is the output of the homonymous command.

In case it cannot be found from within MATLAB, please navigate to the respective "+internal" folder (as in the example path above), and check that the file "getLegendableChildren.m" is actually there.

If the file is not present in this folder, it may be that your MATLAB installation is incomplete. You would then need to re-install it.

If the file is present inside the "+internal" folder, please restore the default path in order to fix your issue. You can do this by executing the following in MATLAB Command Window:

>> restoredefaultpath
>> rehash toolboxcache

After doing so, you should be able to use MATLAB normally. Please check that the issue is fixed, and if that is the case, please save the new MATLAB search path by executing the following command in MATLAB Command Window:

>> savepath

MATLAB: How to call Cygwin command pipeline with the MATLAB ‘system’ function

Disclaimer: Cygwin is a Linux emulator in Windows. Cygwin is not in the supported platform list. This article is meant as a self-help resource for customers with the similar issues.

In this issue, there are several things to understand to find the right solution:

1. The 'system' function of MATLAB only passes the command to the operating system (OS) and has no control over how the passed command is executed.

2. Installing Cygwin does not grant the OS the knowledge to the counterpart executables of the Linux commands. These executables reside under the 'bin' sub-directory under the Cygwin installation directory.

3. Forward slash ('\') works for Windows shell but not for the Cygwin shell.

4. Two single quotes ('''') do not act as a double quote ('"') in the Windows shell.

5. The semicolon (';') works as a pipeline in Cygwin (or real Linux) but not in a Windows shell.

With the above understanding, the code in the question should be revised as below. The primary change is to include the full paths to each invoked Cygwin commands.

>> clear;
>> cygwinPath = 'C:\cygwin\bin'; % the value depends on the actual installation of Cygwin
>> cw_gzip = fullfile(cygwinPath, 'gzip');
>> cw_sed = fullfile(cygwinPath, 'sed');
>> cw_split = fullfile(cygwinPath, 'split');
>> cw_date = fullfile(cygwinPath, 'date');
>> inputfname = 'input.gz';
>> nlines = 5;
>> outprefix = ''
>> system(cw_date); % separate call to 'date' without using ';' for pipeline separation, which is not supported in Windows
>> pipeline = sprintf(...
>>    ['%s -dc %s | '...
>>     '%s -n \"2p;4~2p\" | ' ...
>>     '%s -a 3 -d -l %d --numeric-suffix=1 --additional-suffix=%s '...
>>     '--filter=\"%s > $FILE.gz\" - %s/file'], ...
>>     cw_gzip, name2, ...
>>     cw_sed, ...
>>     cw_split, nlines, '_r2_callqual.txt', ...
>>     strrep(cw_gzip,'\','/'),...
>>     outdir);
>> system(pipeline);
>> system(cw_date);

Best Answer

Related Solutions

MATLAB: Do I get the error “Undefined ‘matlab.gr​aphics.ill​ustration.​internal.g​etLegendab​leChildren​'” when using the function ‘legend’

MATLAB: How to call Cygwin command pipeline with the MATLAB ‘system’ function

Related Question

MATLAB: Do I get the error “Undefined ‘matlab.graphics.illustration.internal.getLegendableChildren'” when using the function ‘legend’