# [R] R's integrate function

Charles C. Berry cberry at tajo.ucsd.edu
Wed Oct 1 00:08:19 CEST 2008

```On Tue, 30 Sep 2008, Susanne Pfeifer wrote:

> Hi,
>
> sorry, I was a bit confused and my function looked slightly different
> from the one I posted before:

In any case, you will not get far trying to integrate this one for values
of z like 12000 without doing some homework. Simply plugging the function
into 'integrate' won't get an accurate answer.

The function you have has a narrow spike with a lot of mass near the
origin when
z=12000.

The answer you got is off by orders of magnitude. (Try changing the limits
of integration to (0,0.1) and compare to what you got with (0,1) to see
this).

You'll need to come up with a better method of finding this integral.

HTH,

Chuck

>
> Susanne Pfeifer schrieb:
>>>> integrate(function(y,z){
>>> +   sapply(y, function(y,z){
>>> + integrate(function(x,z)
>>> +
>>> 1/x*dbeta(0.01,x/(0.005/1.005),(1-x)/(0.005/1.005))*dbeta(y,x/(0.005/1.005),(1-x)/(0.005/1.005))*(1-y)^z,0,1
>>>
>>> +           ,423)\$value
>>> + })
>>> + },0,1,423)
>
> integrate(function(y,z){
> sapply(y, function(y,z){
> integrate(function(x,z)
> 1/x*dbeta(0.01,x/(0.01/1.01),(1-x)/(0.01/1.01))*dbeta(y,x/(0.01/1.01),(1-x)/(0.01/1.01))*(1-y)^z,0,1,12000)\$value
> })
> },0,1,12000)
>
> Sorry for the confusion...
>
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