Re: NIntegrate and Plot

• To: mathgroup at smc.vnet.net
• Subject: [mg95801] Re: NIntegrate and Plot
• From: dh <dh at metrohm.com>
• Date: Wed, 28 Jan 2009 06:25:51 -0500 (EST)
• References: <glethi\$4pp\$1@smc.vnet.net> <glk80f\$o7v\$1@smc.vnet.net> <glmsrg\$mjj\$1@smc.vnet.net>

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Hi Dimitris,

I must have fooled myself, I could actually integrate the function. I

think I got some typo in the input.

Daniel

dimitris wrote:

> On 26 =C9=E1=ED, 13:49, dh <d... at metrohm.com> wrote:

>> Hi Dimitris,

>>

>> integrate your function before plotting it:

>>

>> Integrate[fun[r, t], {t, 0, Infinity}, Assumptions -> {r >= 0}]

>>

>> hope this helps, Daniel

>>

>> dimitris wrote:

>>> Hello.

>>> I have the following function

>>> fun[r_, t_] := -(((-3 + 4*t^2 + 8*t^4 - 8*t^3*Sqrt[1 + t^2])*

>>>       BesselJ[1, r*t])/(3 + 14*t^2 + 24*t^4 + 16*t^6 -

>>>            16*t^3*Sqrt[1 + t^2] - 16*t^5*Sqrt[1 + t^2]))

>>> How can I achieve better performance in the following task

>>> Plot[NIntegrate[fun[r, t], {t, 0, Infinity}], {r, 0, 3}]

>>> Thank you very much.

>

> Hi Daniel and thanks for your response.

> For what reason to use Integrate since Mathematica cannot evaluate

> analytically

> the integral?

>

> Dimitris

>

```

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