ndsolve with discrete, piecewise variable
- To: mathgroup at smc.vnet.net
- Subject: [mg17160] ndsolve with discrete, piecewise variable
- From: "Oscar Stiffelman" <ostiffel at leland.stanford.edu>
- Date: Sun, 18 Apr 1999 00:59:44 -0400
- Organization: SBC Internet Services
- Sender: owner-wri-mathgroup at wolfram.com
Hi, 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). As an analogy, I believe SPICE has the ability to simulate circuits with piecewise time-domain voltages specified for a single node. This is precisely what I want to do in Mathematica, but I would like to do it for systems other than electrical circuits. I appreciate any feedback, advice, etc. Thanks, Oscar Stiffelman Stanford University Computer Science Department, Masters Student in AI