Ken & Mike on the MATLAB Desktop

April 21st, 2008

When the Array Editor was introduced back in MATLAB 5.0, it provided static snapshots of MATLAB double arrays.  It has evolved a lot since then, to provide dynamic editors for…

• One- and two-d arrays of all numeric types
• Logical arrays
• Cell Arrays
• Structures
• Single-line character arrays
• timeseries objects
• viewers for all other objects, including N-D arrays.

A lot of new functionality was added in R2008a, including

• Editors for objects created in the new MATLAB class system
• Improved Structure support
• Support for Data Brushing
• Other interface enhancements.

Because of all of these changes since Version 5, we felt that it was time to rename the Array Editor.  It’s now called the “Variable Editor” to reflect its enhanced capabilities.

Let’s take a look at some of the changes.  Create a variable and open it in the Variable Editor:

>> x = magic(10);

>> openvar x % Or go to the Workspace and double-click on x.

Here we see the Variable Editor with a new information bar bar located just below the toolbar.  It shows the name, size, and class of the current variable, as well as the same icon (based on data type) that’s shown in the Workspace.

We also see the new data brushing toolbar button.  Data brushing is a topic unto itself, worthy of a future posting (stay tuned - if you can’t wait to try it, checkout the documentation).

Structure Editing

We’ve enhanced structure editing to leverage a lot of the features that have been added to the Workspace in recent years.  To see this, let’s create a structure with some interesting data.

>> s.data = magic(10);

>> s.city = ‘Natick’;

>> s.temp = 70.2;

>> openvar s

As you can see, the Variable Editor shows the fields of the structure in the same way that the Workspace shows the variables in the Workspace.  Field (instead of Name), Value, Min, Max, and all of the other columns accessible in the Workspace are also shown here.  Further, all of the gestures for editing (clicks, context menus, and so on) are identical to those used in the Workspace. 

Object Editing

We’ve also added support for MATLAB class system objects.  Now, the public properties of objects are shown in the same way as the fields of structures.

Let’s examine an instance of the memmapfile object:

>> m = memmapfile(which(’clown.mat’));

>> openvar m

Notice that the public properties of the object appear in the Variable Editor.

Normally, only the public properties of an object are visible.  But if you’re debugging an object, you’ll need to be able to get to the protected or private properties, too.  The Variable Editor supports that.  Let’s set a breakpoint in one of the methods of memmapfile, and watch what happens.

>> edit memmapfile

Set a breakpoint on the set.writable method (in R2008a, that’s line 132) by right-clicking on that line and selecting “Set/Clear Breakpoint.”

Now, do something to hit that breakpoint:

>> m.writable = false;

The debugger stops on that line of code.  In the Editor, you can see that the object being debugged is called “obj”.  To see the contents,

>> openvar obj

The Variable Editor opens, showing all of the properties, both public and private.  The ones that end users normally have access to are shown without any lock icons next to them.  In contrast, the private properties have little red locks next to them, to show you that they’re normally inaccessible.  You can only see them because you’re debugging one of the object’s methods.

These enhancements to Variable Editor should help to make interactions with your data more seamless. Let us know which Variable Editor enhancement you use most!

By Bob Gilmore

Bob Gilmore manages the Plotting and Data Exploration development team at The MathWorks. He will be writing occasionally about tools for importing, managing, and exploring data in MATLAB.

06:39 UTC | Posted in Data Tools | Permalink |

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8 Responses to “Variable Editor”

1. chee replied on April 27th, 2008 at 16:33 UTC :
   

   Hi Bob,

   I have a question for using memmapfile.

   We can create an memmapfile object using m = memmapfile(which(’clown.mat’));

   Can we just load a subset (say the first 100 row and cols) of the matrix simply using;
   subset = m.data(1:100,1:100);?

   I tried that but it doesn’t work. Can you suggest how to access the memory mapped matlab file? Thanks.

   Chee

   Can you

2. chee replied on April 28th, 2008 at 02:37 UTC :
   

   Hi Bob,

   The question is still about memmapfile for matlab file:

   The code is as follows:
   mydata = [(1:100)’ (1:100)’];
   save test.mat mydata -v6

   m = memmapfile(’test.mat’,'format’,{’double’,[100 2],’mydata’});
   m.Data
   ??? Error using ==> memmapfile.memmapfile>memmapfile.hCreateMap at 257

   I am wondering how to memory-map a .mat file. I guess there is some header information in the .mat file so that the data cannot be properly accessed.

3. Bob Gilmore replied on April 28th, 2008 at 15:17 UTC :
   

   Chee,
   Sorry, but I don’t know much about MEMMAPFILE. I recommend contacting MathWorks technical support, or posting your question to the comp.soft-sys.matlab Usenet group.
   –
   Bob Gilmore

4. Marcelino Martinez replied on October 30th, 2008 at 05:27 UTC :
   

   Hi,

   I am using varible editor in order to check the values in a big array (more than 280000 rows)

   Is it possible to jump to a specific row or colum in variable editor ?

   Thank you very much

5. Bob Gilmore replied on October 30th, 2008 at 10:13 UTC :
   

   Marcelino,
   Sorry, but that capability isn’t available yet. We have it entered in our enhancement tracking system.

   Thanks for asking,
   —
   Bob Gilmore

6. Daniel replied on September 17th, 2009 at 07:00 UTC :
   

   Hi,

   I use Matlab R2008b, but I cannot see the private members of the obj I’m debugging. Are there any additional settings to be made in order to make them visible in the variable editor?

   Daniel

7. Ryan replied on September 21st, 2009 at 13:36 UTC :
   

   Hi,

   I find the variable editor very useful now that it is possible to view my own objects. There seems to be a problem using dependent properties however. It seems that if I have more than a couple of them, none of my objects properties show in the Variable Editor anymore. Is there a way around this? I cannot find any documentation to suggest what I am doing wrong.

8. Mike replied on September 21st, 2009 at 14:58 UTC :
   

   Ryan,

   There shouldn’t be a limit to the number of dependent properties that can be displayed (other than maybe system resources). Since this occurs for you at some variable point, I would suggest first talking to technical support to see if they can recommend a workaround:
   http://www.mathworks.com/support/service_requests/contact_support.do

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<pre class="code">
a = magic(3);
sum(a)
</pre>

These postings are the author's and don't necessarily represent the opinions of The MathWorks.