New Features
in
DFIELD & PPLANE
for
MATLAB version 5

Version 5 of MATLAB comes with new programming tools that make it much easier to program small routines such as DFIELD5 and PPLANE5. These facilitated the installation of a variety of new features. The programs have been entirely rewritten to take advantage of version 5.

As a result there are differences in the appearance from version 4. However, the basic functionality is the same as before. The manual Ordinary Differential Equations using MATLAB should still be useful. It will be necessary to search for the old options under a larger number of menus. There are new options as well.

These versions have now been used in a fairly large number of courses at a variety of institutions. They seem to be pretty well bug free. Even so, any feedback would be greatly appreciated.

New features common to both.

New names. The new versions are called DFIELD5 and PPLANE5 to distinguish them from the old versions. In some situations (including the student network at Rice) it will be necessary to keep both available for a while. This change will make that possible.

New look. Most of the new look is due to the redesigned user interface controls in MATLAB ver.5. However an effort has been made to obtain a good appearance of everything on all platforms. The display figures now have white backgrounds instead of black (see Figure 1. below). If you prefer the old black backgrounds, start the programs with the parameter 'black', e.g., dfield5('black'). If you are using a black and white monitor, the routines will adapt automatically.

Figure 1. The DFIELD5 Display Window using the default background option.

Error trapping. An effort has been made to detect all the errors a user might make in entering data. These are responded to by error messages that are specific to DFIELD5 or PPLANE5. Hopefully they are more useful than the standard MATLAB error messages. The goal is to prevent any MATLAB error messages from appearing. Without doubt we have failed, and this goal may well be unattainable, but we want to hear about any untrapped messages.

Speedier startup. MATLAB now gives the user the option to speed up the start of functions by creating pre-parsed pseudo-code files (P-files). This is done using the command pcode, and it should definitely be applied to DFIELD5 and PPLANE5.

Menus. All associated windows now have menus. Of course it is now standard for all windows to have menus in MATLAB, but those in DFIELD5 and PPLANE5 are designed especially for these applications. The organization of the choices is different than it is in the older versions. Hopefully users will find the new organization more intuitive.

One nice feature that occurs in any window which a user might want to print, is three print options in the File menu. One will print that figure, without the user interface controls. The other two are now standard in MATLAB. One allows the user to set the page position of the printed figure, and the other allows the user to choose between several different print options, including choosing to make postscript files of the figure.

Figure 2. The PPLANE5 Display Window using the 'black' background option. The red solution curve is still being computed. Notice the Stop button in the upper right hand corner.

The Stop button. Both routines now have Stop buttons that can be used to stop the computation of a solution. Pushing the Stop button only stops the computation in one direction, so to stop a solution completely it might be necessary to click the button twice.

Message windows. Both routines now have message windows on the bottom of the Display Windows. Most of this information used to go to the Command Window, but many users did not even notice it. The information is especially useful in PPLANE5, where the computation is stopped by the program detecting one of the Poincare Bendixson alternatives.

New solvers.

New options in keyboard input. It is now possible to specify a computation interval in the Keyboard Input Window. The initial point can be anywhere in the interval. Using a prescribed computation interval disables the stopping criteria, and permits the solver to compute over a larger interval than would otherwise be possible.

New options for Zooming.

Prettier titles.

Easy use of larger fonts and windows.

No more funny files. Do you have lots of files of the form dftp*.m and pptp*.m cluttering up your computer? These were put there by earlier versions of DFIELD and PPLANE. This will no longer happen with the new versions. At the most there will be one or two, but these will be eliminated the next time that the new versions are started up. If you systematically quit from MATLAB before you stop your computer there will never be such files left behind.

If you do have such a collection of old files, the new versions will remind you that they can be safely deleted. After you delete these useless files, DFIELD5 and PPLANE5 will take care of the problem in the future.

New feature in DFIELD5.

One of the goals in the design of DFIELD is to make it simple and easy to use. At Rice we want our students to be able to use it during the first week of the course --- even those students who are computer-phobic. For that reason we have resisted the urge to add a lot of new feautres. Except for the stylistic changes that have been made in both DFIELD5 and PPLANE5, there is only one new feature in DFIELD5.

The phase line. Many new textbooks are stressing the phase line. It is now possible to have a phase line in the Display Window by choosing it from the Options menu. The line will be drawn near the left border of the display rectangle. As an orbit is computed and plotted a dot will follow the motion along the phase line.

Figure 3. The DFIELD5 Display Window with the phase line on the left. The red color and the presence of the Stop button indicates that the backward solution is still being computed.

New features in PPLANE5.

PPLANE keeps getting fancier. Perhaps it is suffering from feature creep. However, these changes seemed to be called for. In fact in most cases there were users who called for them.

Nullclines.

Saving and loading systems and galleries. In response to user demand, the capability of saving systems to the disk, and then loading them into PPLANE was added some time ago. This capability has been expanded in PPLANE5. It is now possible to save and load entire galleries as well as systems. These options are contained in items in the File menu in the Setup Window. The user now has complete control over the gallery menu.

The options to Load a system and especially to Load a gallery can be somewhat slow. The reason is that each system added is compared to the systems already in the gallery. This prevents duplicate systems from being loaded. It also detects duplicate names for different systems. The user is prompted for appropriate action when duplications are discovered.

Linearizations.

Cropping t-plots. In any of the three 2-dimensional plots, the t-axis can be cropped. To do do select a rectangle by dragging the mouse. This will result in an outlined rectangle in the figure, and the Crop button becoming enabled. If you like the choice, click on Crop, and a new t-plot will appear with that choice of an interval for the independent variable. If you do not like the choice, make another. If you just click the mouse, everything will be undone.

Notice that only the interval for the independent variable is affected by cropping. The other variables are unaffected.

Rotating the 3D t-plot. Just click the mouse and drag. This option is not available in the composite plot because that view is too complicated for a rotation to effectively show anything useful.


John C. Polking <polking@rice.edu>
Last modified: Fri Jan 28 14:56:13 CST 2000