       Re: numeric integration

• To: mathgroup at smc.vnet.net
• Subject: [mg81158] Re: numeric integration
• From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
• Date: Fri, 14 Sep 2007 03:37:00 -0400 (EDT)
• Organization: The Open University, Milton Keynes, UK
• References: <fcb40h\$fm3\$1@smc.vnet.net>

```C. Seja wrote:

> I'd like to intergate a function f with NIntegrate:
> NIntegrate[f[x], {x, 0, 0.1}]
>
> But this doesn't work if, i.e.
>
> f = NIntegrate[Sin[x + #], {x, 0, 1}] &
>
> It will give a wrong result (0.7 instead of 0.05). Why? I mean, I can
> evaluate f at any point without problems, i.e. f[0.1] gives 0.37.

In:= f = NIntegrate[Sin[x + #], {x, 0, 1}] &;
f[0.1]

Out= 0.541408

> So why doesn't
>
> NIntegrate[f[x], {x, 0, 0.1}]
>
> work? It doesn't even give a warning! So, is there a proper way to do this
> (without using one two-dimensional NIntegrate)?

In:= f[y_?NumericQ] := NIntegrate[Sin[x + y], {x, 0, 1}]

In:= f[0.1]

Out= 0.541408

In:= NIntegrate[f[y], {y, 0, 0.1}]

Out= 0.050097

Regards,
--
Jean-Marc

```

• Prev by Date: Re: Optimization with symbolic paramters
• Next by Date: HELP!
• Previous by thread: Re: numeric integration
• Next by thread: Re: numeric integration