Re: Evaluating integral with varying upper limit?
- To: mathgroup at smc.vnet.net
- Subject: [mg71054] Re: Evaluating integral with varying upper limit?
- From: "dimitris" <dimmechan at yahoo.com>
- Date: Wed, 8 Nov 2006 05:59:59 -0500 (EST)
- References: <eimqg9$b9k$1@smc.vnet.net>
It will be very helpful if you give your function f[x]
Regards
Dimitris
AES wrote:
> Given a function f[x] which happens to be rather messy and not
> analytically integrable, I want to evaluate the function
>
> g[y_] := NIntegrate[f[x], {x, ymin, y} ]
>
> with ymin fixed and ymin < y < Infinity.
>
> I suppose that FunctionInterpolate is the way to go here (???).
>
> But, are there tricks to tell FunctionInterpolate what I know in
> advance, namely that f[x] is everywhere positive, and decreases toward
> zero rapidly enough at large x that g[y] will approach a finite limiting
> value as y -> Infinity? (which value I'd like to have FI obtain with
> moderate accuracy -- meaning 3 or 4 significant digits, not 10 or 20)
>
> Thanks . . .