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MathGroup Archive 2007

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FindRoot and NIntegrate

  • To: mathgroup at smc.vnet.net
  • Subject: [mg81850] FindRoot and NIntegrate
  • From: mfedert at gmail.com
  • Date: Fri, 5 Oct 2007 04:44:01 -0400 (EDT)

Hi all,

I have what is probably a very simple problem.  I want to find x which
solves an equation of the form

\integral f(x,y) dy = 0

I have tried something along the lines of

FindRoot[ NIntegrate[ f(x,y) , {y, -inf, inf} ], {x, x_0 } ]

but it doesn't work ---- my theory being that NIntegrate tries to go
ahead and do the numerical integration before it knows what x is equal
to... which blows up  because the integrand is - as a function of x -
non-numerical... Is there a way around this?  I'm sure there's some
trivial modification I can make to get things working again.

Thanks, in anticipation ---
MF



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