Re: ndsolve with discrete, piecewise variable
- To: mathgroup at smc.vnet.net
- Subject: [mg17188] Re: ndsolve with discrete, piecewise variable
- From: Eckhard Hennig <hennig at itwm.uni-kl.de>
- Date: Tue, 20 Apr 1999 01:21:01 -0400
- Organization: ITWM
- References: <7fboro$98u@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Oscar Stiffelman wrote in message <7fboro$98u at smc.vnet.net>... >Can anyone tell me if NDSolve can be used for the following problem? > >I would like to construct a system of differential equations and then use a >list of data points (piecewise) as the value of one of the variables. > >For example, I might want to build a filter (electrical) where the input >could be any arbitrary signal, not just a clean mathematical signal. I >would like to see the system's response (time-domain value of a specific >variable) to the input values. > >Is it possible to evaluate this in a discrete manner? For example, could I >solve the system using NDSolve and then use the interpolating function in >the following manner: > >1. set the "input" variable equal to the first element in the list, and set >the other variables equal to some arbitrary starting condition (i.e. zero) >2. evaluate the system using the interpolating function, saving the values >of every variable >3. set the "input" variable equal to the next element in the list, and set >the other variables equal to the saved value, and goto 2. > >I would prefer, however, to treat the data points as if they were discrete >samples of a continuous function, and for Mathematica to generate continuous >response (also discretely sampled, of course). Dear Oscar, take a look at the notebook "Distortion.nb" at http://www.itwm.uni-kl.de/as/products/ai/demos.html To run the demo you need a copy of our circuit analysis toolbox Analog Insydes. A time-limited, fully functional evaluation version is available for download from our web site. http://www.itwm.uni-kl.de/as/products/ai Best regards, Eckhard ----------------------------------------------------------- Dipl.-Ing. Eckhard Hennig mailto:hennig at itwm.uni-kl.de Institut fuer Techno- und Wirtschaftsmathematik e.V. (ITWM) Erwin-Schroedinger-Strasse, 67663 Kaiserslautern, Germany Voice: +49-(0)631-205-3126 Fax: +49-(0)631-205-4139 http://www.itwm.uni-kl.de/as/employees/hennig.html ITWM - Makers of Analog Insydes for Mathematica http://www.itwm.uni-kl.de/as/products/ai -----------------------------------------------------------