RE: Coupled Differential Equations

*To*: mathgroup at smc.vnet.net*Subject*: [mg34775] RE: [mg34751] Coupled Differential Equations*From*: "Curt Fischer" <cfisher at bio.titech.ac.jp>*Date*: Thu, 6 Jun 2002 01:54:58 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

Dear Cyrill, You didn't give very many details of your problem. Therefore I am unsure if my answer will help you or not. >From: Cyrill Slezak [mailto:slezakcy at physik.uni-augsburg.de] To: mathgroup at smc.vnet.net >Subject: [mg34775] [mg34751] Coupled Differential Equations > >I understand that NDSolve will solve a set of first order coupled. >diff.eqn. >Here is my problem: I have a set of 20+ equation that all have the exact >same structure and I can't seem to find an easy way to input them. For >any help I'd be highly appreciative. >The equations are of the form > >d V_k(l)/d l = V_k(l) + Sum[ V_k'(l), (k not equal k')] > >where k is the number of diff. eqn. Using the function Table[] is one way to do this: In[1]:= n = 20; eqns = Table[\(v\_k'\)[l] == v\_k[l] + \ Sum[If[kp == k, 0, \(v\_kp'\)[l]], {kp, 1, n}], {k, 1, n}] In[2]:= vars = Table[v\_k[l], {k, 1, n}] In[3]:= DSolve[eqns, vars, l] I used "kp" instead of your "k'". Hope this helps you. Curt Fischer Dept. of Bioengineering Tokyo Institute of Technology