DFIELD & PPLANE
MATLAB version 5
Version 5 of MATLAB comes with new programming tools that make it much
easier to program small routines such as
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.
PPLANE5to 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
dfield5('black'). If you are
using a black and white monitor, the routines will adapt
DFIELD5Display 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
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.
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
and it should definitely be applied to
Menus. All associated
windows now have menus. Of course it
is now standard for all windows to have menus in MATLAB, but those in
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.
PPLANE5Display 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
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.
Easy use of larger fonts and windows.
No more funny
files. Do you have lots of files of the form
pptp*.m cluttering up your computer? These were put
there by earlier versions of
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
PPLANE5 will take
care of the problem in the future.
DFIELDis 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
PPLANE5, there is only one new feature in
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.
DFIELD5Display 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.
PPLANEkeeps 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.
Saving and loading
systems and galleries. In response to user
demand, the capability of saving systems to the disk, and then loading
PPLANE was added some time ago. This
capability has been expanded
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
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.
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.