bug in [detools,dchangevar] in maple v.4 (8.9.97)

Georges Thomas


Maple R4 answers:


I expected:


In the online help about Dchangevar, the first example in ”Examples/Additional examples” gives:


Maple answers, after some simplication:


Answer expected:


It seems that Dchangevar mistakes if the order of the differential equation is >=2 and if the change of variable is not linear.

Is there a bug in Maple or in my mind?

The bug is removed in Maple V Release 5. (U. Klein)

Edgardo S. Cheb-Terrab (9.9.97)

As an alternative, you can use PDEtools[dchange], which is able to perform non-linear changes of variables and also in PDEs. In your example,


PDEtools is a package distributed in the Share Library of Maple R4. The last version of PDEtools is found at

http://lie.uwaterloo.ca/pdetools.html (Canada)

or

http://dft.if.uerj.br/pdetools.html (Brazil)

Preben Alsholm (10.9.97)

I get the same as you do! There must be a bug in Dchangevar.

Juergen Boehm (11.9.97)

I checked the variable transformation with a procedure of my own ( vsubs ) and could confirm the supposed results of G. Thomas and also reproduce the wrong answers that Dchangevar gave :


Yuri Muzychka (12.9.97)

I have noticed the bug in DEtools a long time ago. I had sent Maple a worksheet summarizing where the bug occurs, but never received any follow up.

If I recall, what I had observed was that DEtools did not know how to apply the chain rule properly.

I discovered this while trying to get maple to perform the same set of calculations I had done on paper. Had the change of variable worked properly, I would have reduced my ODE to one which has the hypergeometric function as a solution. Otherwise, Maple could not solve it. I was trying to reproduce some work I had found in a paper I was using for my research.