Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
2007
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 2007

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

Search the Archive

FindRoot[ NIntegrate[...] ...] works but generates "NIntegrate::nlim" limit error message!?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg72493] FindRoot[ NIntegrate[...] ...] works but generates "NIntegrate::nlim" limit error message!?
  • From: "William McHargue" <William at McHargue.Org>
  • Date: Tue, 2 Jan 2007 04:17:19 -0500 (EST)

Hello,

I wish to solve for an integration result to equal a given value while
varying the upper limit of the integration. It seems a straightforward
thing to do, and in fact it finds the numerical answer, but it
generates an error message at the beginning of the root solving
operation. I create a function to perform a numerical integration with
a passed upper limit of integration:

In[1]:= integralFunction[upperLimit_] := NIntegrate[x, {x, 0,
upperLimit}]


Then I create a function to find a result of this integration that
equals a supplied value with the upper limit of integration as the
independent variable:

In[2]:= rootOfIntegralFunction[solveForValue_] :=
FindRoot[integralFunction[u] == solveForValue, {u, 1},
EvaluationMonitor :> Print[u]]


(I use the EvaluationMonitor to print the value of "u" as it searches
for the solution.)

When I execute the following I get an error message, yet it finds the
correct result:

In[3]:= rootOfIntegralFunction[12.5]

   NIntegrate::nlim : x = u is not a valid limit of integration.
More...

1.

13.

2.2

6.78182

4.3982

5.04117

5.00017

5.

5.

Out[3]= {u->5.}



If anyone has any insight into this behavior please let me know. Thank
you!

Bill.


  • Prev by Date: please explain why numerical integration is attempted for this input
  • Next by Date: please explain why numerical integration is attempted for this input
  • Previous by thread: Re: please explain why numerical integration is attempted for this input
  • Next by thread: FindRoot[ NIntegrate[...] ...] works but generates "NIntegrate::nlim" limit error message!?