# [R] analytical solution to Sum of binominal distributed random numbers?

Rainer M. Krug rainer.r at krugs.de
Wed Oct 24 10:13:40 CEST 2007

```Frede Aakmann Tøgersen wrote:
> Perhaps
>
>
> is something that you can use?

Thanks a lot - that might help.

Rainer

>
>
>
> Best regards
>
> Frede Aakmann Tøgersen
> Scientist
>
>
> UNIVERSITY OF AARHUS
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>> -----Oprindelig meddelelse-----
>> Fra: r-help-bounces at r-project.org
>> [mailto:r-help-bounces at r-project.org] På vegne af Rainer M Krug
>> Sendt: 24. oktober 2007 09:11
>> Til: Charles C. Berry
>> Cc: r-help
>> Emne: Re: [R] analytical solution to Sum of binominal
>> distributed random numbers?
>>
>> Hi Charles
>>
>> thanks for the pointing out that size and prob can be vectors
>> as well - I tried it out but used 1 as the number of
>> observations, assuming that and it only gave me one randon
>> mumbewr (as it should be but not expected).
>>
>> But I was more looking at a analytical solution, as I have to
>> sum up a huge number of random numbers. But I am going to try
>>
>> Thanks
>>
>> Rainer
>>
>>
>> Charles C. Berry wrote:
>>>  	?rbinom
>>>
>>> only says:
>>>
>>>      size: number of trials (zero or more).
>>>
>>>      prob: probability of success on each trial.
>>>
>>>
>>> But they can be vectors.
>>>
>>> BTW, you were aked to "PLEASE ... provide  minimal, self-contained,
>>> reproducible code."
>>>
>>> What you show cannot run without correction.
>>>
>>> Most likely, you intended size(n) to be the n-th element of
>> the vector
>>> 'size', which in R is written 'size[ n ]' .
>>>
>>> In which case
>>>
>>>  	sum (rbinom( length(prob) , size, prob ) )
>>>
>>> works.
>>>
>>> Chuck
>>>
>>> On Tue, 23 Oct 2007, Rainer M Krug wrote:
>>>
>>>> Hi
>>>>
>>>> I have two vectors, prob and size, and I want to add the random
>>>> deviates  of these two, i.e.
>>>>
>>>> sum(
>>>>   sapply(
>>>>          1:length(prob),
>>>>          function(n){ rbinom(1, size(n), prob(n) }
>>>>         )
>>>> )
>>>>
>>>> My problem is that I have to do this for a large number of value
>>>> combinations. Is there a faster way of doing this?
>>>>
>>>> Rainer
>>>>
>>>> ______________________________________________
>>>> R-help at r-project.org mailing list
>>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>>> http://www.R-project.org/posting-guide.html
>>>> and provide commented, minimal, self-contained, reproducible code.
>>>>
>>> Charles C. Berry                            (858) 534-2098
>>>                                              Dept of
>> Family/Preventive Medicine
>>> E mailto:cberry at tajo.ucsd.edu	            UC San Diego
>>> http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego
>>> 92093-0901
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
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