MathGroup Archive 2008

[Date Index] [Thread Index] [Author Index]

Search the Archive

Controlling the order of evaluations

  • To: mathgroup at
  • Subject: [mg92985] Controlling the order of evaluations
  • From: anguzman at
  • Date: Wed, 22 Oct 2008 05:37:23 -0400 (EDT)

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:


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 
By the way, I already tried:
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.

  • Prev by Date: Re: Is there a simple way to transform 1.1 to 11/10?
  • Next by Date: Re: FindMinimum constraints
  • Previous by thread: Re: Executing an external notebook within another notebook
  • Next by thread: Re: Controlling the order of evaluations