RE: Question from a biologist

*To*: mathgroup at smc.vnet.net*Subject*: [mg70457] RE: [mg70410] Question from a biologist*From*: "David Park" <djmp at earthlink.net>*Date*: Tue, 17 Oct 2006 02:58:15 -0400 (EDT)

The trouble with your posting is that you don't tell us anything about how you generate your differential equations, or how many variables and parameters you have. There are certainly ways to generate differential equations and distinguish the parameters from the variables. You might be able to use a statement like SetAttributes[{p1, p2, p3}, Constant] before you generate the ODEs. Or, if you already have the equations you could use a rule. deqns2 = deqns1 /. {p1'[_] -> 0, p2'[_] -> 0, ...} David Park djmp at earthlink.net http://home.earthlink.net/~djmp/ From: tnad [mailto:terry_najdi at hotmail.com] To: mathgroup at smc.vnet.net I'm trying to simulate some chemical reactions in mathematica using ODEs. I want to keep some of the variables (the parameters in the differential equations) constant during the simulation. Right now, I have to look for the first derivative of every variable in a sea of differential equations and set it to zero. Is there a more "elegant" way to do this in mathematica?