RE: trying to evaluate a piecewise function

*To*: mathgroup at smc.vnet.net*Subject*: [mg2156] RE: [mg2114] trying to evaluate a piecewise function*From*: "John R. Fultz" <jfultz>*Date*: Tue, 10 Oct 1995 02:37:33 -0400

If you have variables exprs and subdomains defined like so: exprs={x, x^2, 2x}; subdomains={0<=x<1,1<=x<2,2<=x<=5}; then, you could do: whichlist=Flatten[Transpose[{subdomains,exprs}]] which returns: 2 {0 <= x < 1, x, 1 <= x < 2, x , 2 <= x <= 5, 2 x} Note that this is the exact format required as the arguments to Which. So, you can use the Apply command (or its shorthand equivalent, @@) to apply Which to the list and create a function which can easily be plotted. Plot[Which @@ whichlist, {x, 0, 5}] Hope this helps! Sincerely, John Fultz Technical Support ---------- From: Alberto.MERONI[SMTP:Alberto.Meroni at th.u-psud.fr] Sent: Wednesday, October 04, 1995 12:53 AM To: mathgroup at smc.vnet.net Subject: [mg2114] trying to evaluate a piecewise function I am trying to solve this problem: I have a list of expressions {expr1,expr2,...exprN} each valid in a subdomain specified as a list {l1<x<=u1,l2<x<=u2.. ,lN<x<=uN} and I would like to have a function which evaluate a plot this piecewise object. 1) Everything is continous 2) The union of all subdomains exhaust the domain l1<x<=uN 3) The number N is a given parameter (of order 10) 4) I would not like for each value of N to enter something like If [clause1,expr1,....] Somebody has a way to do this ? I could not find a solution in the Book. For information this thing comes from the following problem: You are given a list of points and you want to find a piecewise continous approximation to these values. It is related to the so called multicanonical technique of Monte Carlo simulation. Thank you very much Alberto Meroni ameroni at psisun.u-psud.fr