Here are the new PDE2D 9.1 features:

1. For 3D problems, the MATLAB postprocessing program now draws a picture of the 3D region, then draws P1,P2 or P3=constant cross-sections in 3D space, with color used to indicate the solution values (see example ). This represents a big improvement over PDE2D 9.0 for visualization of 3D solutions.
2. 1D equations can now include Dirac Delta source terms, when the Galerkin method is used. This was already possible when solving 2D problems, with the Galerkin method.
3. A third example has been added to the GUI documentation: a 1D time- dependent damped wave problem (see screendump ).
4. The GUI now generates surface plots as well as contour plots, for 2D and 3D problems. For 1D time-dependent problems, plots at individual times are now made, in addition to the x-t surface plots already produced.
5. Three minor bugs/design flaws were fixed:
   1. The output array UOUT (all dimensions) previously was dimensioned differently in the main program and in the postprocessing subroutine POSTPR, where its contents are documented. This created some confusion for users attempting to write out or otherwise postprocess the solution in the main program.
   2. Previously, an error resulted if a parameter named "Z" were used in a 2D collocation problem. (The GUI and interactive driver allow Z as a parameter for 2D problems, as they should, but this previously resulted in a compiler error.)
   3. Previously there were sometimes problems with the MATLAB plots produced by PDE2D (all dimensions), when a time-dependent problem was terminated early due to an integral exceeding its user-specified limit (SLIM8Z or BLIM8Z).