Re: Controlling the order of evaluations

*To*: mathgroup at smc.vnet.net*Subject*: [mg93009] Re: Controlling the order of evaluations*From*: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>*Date*: Fri, 24 Oct 2008 02:26:11 -0400 (EDT)*Organization*: Uni Leipzig*References*: <gdms84$en$1@smc.vnet.net>*Reply-to*: kuska at informatik.uni-leipzig.de

Hi, f[x_?NumericQ, y_?NumericQ] := NIntegrate[2^(s*x), {s, 0, y}] Plot[f[x, #] & /@ {2, 3, 4, 5}, {x, 0.5, 1.5}, Evaluated -> True] ?? Regards Jens anguzman at ing.uchile.cl wrote: > Hello: > Several times I have faced similar problems to this one: > > Suppose I have a function f[x,y] well defined only in numbers, I mean, > it drops errors if I try to evaluate symbols. You could suppose that > is a function that include numerical integration in its definition... > > What I want to do is plotting several curves f[x,y1], f[x,y2],...f[x,yn] > with x as abscissa for specific (and fixed) values of y in the same plot. > > So, what I always end up trying is something like: > > > Plot[f[x,#]&/@{y1,y2,....,yn},{x,a,b}] > > > Mathematica (5.2 Version for Windows) complains but finally interprets > correctly what I meant and does the plot correctly (sometimes)with all > the curves , but this errors are annoying. They are always of the form: > > \" bla bla.. f[x,y1] is not numerical at ....\" > > > > I would be very gratefull if somebody could explain me (or just give > the solution to this thing) the correct order of Holds, HoldFirsts, > HoldPatterns , Evaluate , Unevaluated etc... that make Mathematica > happy. > By the way, I already tried: > Plot[Evaluate[f[x,#]&/@{y1,y2,....,yn}],{x,a,b}] > but didn=B4t work. > > I=B4ll give an specific example: > > f[x_, y_] := NIntegrate[2^(s*x), {s, 0, y}] > > Plot[Evaluate[f[x, #] & /@ {2, 3, 4, 5}], {x, 0.5, 1.5}] > > Generates the 4 curves after giving errors like: > > \"NIntegrate::\"inum\" \"Integrand 2^(s*x) is not numerical at s = 1. \" > > So what I want to do is that the x of the Plotting evaluation enters > f[x,y] before f even sees the x and start freaking out. > > Thanks in advance > > Atte. Andres Guzman > > ---------------------------------------------------------------- > This message was sent using IMP, the Internet Messaging Program. > >