Re: question about NIntegrate

• To: mathgroup at smc.vnet.net
• Subject: [mg128743] Re: question about NIntegrate
• From: Bill Rowe <readnews at sbcglobal.net>
• Date: Fri, 23 Nov 2012 03:25:13 -0500 (EST)
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• Delivered-to: l-mathgroup@wolfram.com
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On 11/22/12 at 4:33 AM, dsmirnov90 at gmail.com wrote:

>I want to use function NIntegrate to integrate a rather complicated
>function which should be calculated numerically and returns a Table.
>However, when I write something of the kind:

>Clear[f] f[(a_)?NumericQ] := {a^2}; NIntegrate[f[x], {x, -1, 1}]

>I get an error: "Integrand f[x] is not numerical at {x} =
>{-0.984085}"

>Strangely, the following code works fine:

>NIntegrate[f[1], {x, -1, 1}]

>giving the result {2.}

>What am I doing wrong?

Is there a reason you have defined f to return a list rather
than a number? This works:

In[7]:= Clear[f]
f[a_?NumericQ] := a^2
NIntegrate[f[x], {x, -1, 1}]

Out[9]= 0.666667

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