My very first post on this blog showed how to change Matlab’s command-window colors. In that post I promised to write another post detailing how system preferences can be changed from the command line.

Last week I wrote about undocumented GUIDE features. After my initial post, I realized that I forgot to mention all the different relevant system preferences that can also be modified. I therefore modified last week’s post with the preferences information. I now wish to finally detail how such preferences can be changed programmatically, from within your Matlab application or from the Matlab desktop command prompt.

Matlab’s user preferences are stored in the matlab.prf text file which is stored in the user’s Matlab preferences folder:

edit(fullfile(prefdir,'matlab.prf'));

Each preference appears to be on a separate line in the following format: <pref-name>=<pref-type><pref-value>

where <pref-type> appears to be one of these:

- ‘B’ => boolean/logical flag
- ‘C’ => color (RGB numeric value)
- ‘F’ => font (type,size,name)
- ‘I’ => int16
- ‘J’ => int64
- ‘R’ => rectangular area (x,y,h,w)
- ‘S’ => string/char

Examples:

EditorShowLineNumbers=Btrue

EditorMaxCommentWidth=I120

You can read the preference names from this matlab.prf file and then use the following (you-guessed-it) java calls to get/set the values:

com.mathworks.services.Prefs.get<type>Pref(<pref-name>) com.mathworks.services.Prefs.set<type>Pref(<pref-name>, newValue);

where <type> is one of: Boolean, Color, RGBColor, Font, Integer, Rectangle, String, Double (I believe Doubles get converted to int64 – possibly a bitwise casting since both use 64 bits)

For example:

com.mathworks.services.Prefs.getBooleanPref('LayoutSnapToGrid') com.mathworks.services.Prefs.setIntegerPref('LayoutGridWidth', 25)

adding a second argument to get<type>Pref() appears to indicate a default value that is returned if <pref-name> is not defined:

com.mathworks.services.Prefs.getIntegerPref('xxxx',123) => 123

We can programmatically set any preference key we like – we are not limited to Matlab’s built-in set. I used this feature in my CPRINTF utility, to set user-defined colors for later use by the desktop’s UI syntax-highlighting engine. The relevant code segment is this:

% Convert a Matlab RGB vector into a known style name (e.g., '[255,37,0]') function styleName = getColorStyle(rgb) % Convert Matlab RGB array into a Java Color object intColor = int32(rgb*255); javaColor = java.awt.Color(intColor(1), intColor(2), intColor(3)); % Preference key name format: '[RRR,GGG,BBB]' styleName = sprintf('[%d,%d,%d]',intColor); % Set/update the preference with this Java Color com.mathworks.services.Prefs.setColorPref(styleName,javaColor);

…which in turn adds entries such as the following to my matlab.prf file:

[12,34,67]=C-15982013

Note that -15982013 = 0xFF0C2243, which is the RGB value [12,34,67] with an opaque alpha value. This value can later be retrieved using:

>> com.mathworks.services.Prefs.getColorPref('[12,34,67]') ans = java.awt.Color[r=12,g=34,b=67]

Warning: I published much of this information on the CSSM forum back in 2007. Ben Steiner then shared his experience on that thread that:

For anyone else that’s playing with this: I don’t advise trying to edit the matlab.prf via matlab(!). I created a situation that made Matlab unworkable. I did find that deleting the matlab.prf completely (in frustration) solved it.

Take a look at your matlab.prf file – can you spot any interesting preference? If so, please share it in the comments section below.

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Hi Yair,

I work on multiple projects at the same time and I like to have multiple matlab instances open on my computer, one for each project (I realize this might not be a particularly smart way to work). However, I would like each of them to save to a different command window history file. Is there a good safe way to do this?

Thanks! All the best,

Shaul

@Shaul – I do not know a way to customize the history file path

Is there a way to programmatically update the Simulink preferences, such as the Autosave option?

Thanks,

paul

@Paul – I’m sure there is, but I don’t know…

Hi Yair,

It seems that after doign this, I need to re-start MATLAB before the changes take effect. Do you know of any better way to make my changes “kick in”?

@Chad – there is a

`com.mathworks.services.Prefs.`

method, but I think it will not help you much because I think that most preferences are loaded and used during startup, not dynamically.load()I just learned once more that it’s extremely helpful to programmatically check for the correct “MatfileSaveFormat” property to avoid being unable to save (or later: load) your results. Thanks for your helpful post!

To change Parallel Pool settings:

To complete the picture:

Hi Yair,

Thanks for this article!

I took inspiration from it to create a package to import and export color schemes in MATLAB. This definitely would not have been possible without undocumentedmatlab!

It is available on GitHub and FileExchange.

All the best,

Scott

Thank you!

Hi Yair,

I was looking for a way to change the setting of the system using matlab when I saw this post.

I wonder if you can help me with it.

I’m connecting two monitors and I want to run a program from one monitor and make it run on the other one.

In the process I need to change setting from ‘screen resolution’ in the control panel.

Could this be done with matlab?

I would appreciate any help.

Thanks,

Parvaneh

@Parvaneh – you will need to check the web for a utility that has a command-line interface that does what you want, and then you can call that utility from Matlab using the

command.system