NIntegrate and Delayed Functions

*To*: mathgroup at smc.vnet.net*Subject*: [mg44121] NIntegrate and Delayed Functions*From*: "Mukhtar Bekkali" <mbekkali at hotmail.com>*Date*: Thu, 23 Oct 2003 07:15:30 -0400 (EDT)*Organization*: Iowa State University*Sender*: owner-wri-mathgroup at wolfram.com

Hi all: I have a function f[x,t] which does not have an explicit integral over t, only numerical integral exists. Suppose F[x] is an integral of f[x,t] over t where t ranges from 0 to some function r[x]. I need to plot F'[x] or the first derivative of F[x] as a function of x (let's call it G[x]). I tried to use Integrate but Mathematica cannot handle it for some functional forms of f[x,t] so I am trying to use NIntegrate as a delayed function to speed up the evaluation. However, I receive an error message that the limit of integration cannot be z[x] and an empty graph. Here is the exerpt from my code: G[x_]:=D[NIntegrate[f[x,t],{t,0,z[x]}],x]; Plot[G[x],{x,0,1}] What am I doing wrong? Of course all functions,- f[x,t], z[x] have a specific form.