# [R] sum of grouped elements of vector

Ivan Kasanický kasanicky.ivan at gmail.com
Fri Jan 23 10:44:39 CET 2015

```Hi Kathryn,
another solution would be to use tapply function. So the code to
create new1 vector would be:

a <- 1:8
fc <- c('g1','g1','g2','g3','g3','g3','g4','g4') # definitions of
groups to sum over
tapply(a,fc,sum)

ivan

On Fri, Jan 23, 2015 at 10:32 AM, Bert Gunter <gunter.berton at gene.com> wrote:
> If Jim's answer is not what you want, then I would say it is because
> your question is too vague to be answered. In particular, how do you
> specify the elements of the vector that are to be summed to create the
> new vectors? ?tapply might then be relevant here, but that's just a
> guess.
>
> -- Bert
>
>
>
>
>
> Bert Gunter
> Genentech Nonclinical Biostatistics
> (650) 467-7374
>
> "Data is not information. Information is not knowledge. And knowledge
> is certainly not wisdom."
> Clifford Stoll
>
>
>
>
> On Fri, Jan 23, 2015 at 12:45 AM, Kathryn Lord
> <kathryn.lord2000 at gmail.com> wrote:
>> Dear R users,
>>
>> I have a quick quesiton.
>>
>> Here is a vector "a".
>>
>> a<- c(1,2,3,4,5,6,7,8).
>>
>> (In fact, I have a huge vector.)
>>
>>
>> With "a", I'd like to create new vectors, for example,
>>
>> new1 = (1+2, 3, 4+5+6, 7+8)
>> new2 = (1, 2+3+4+5+6+7, 8)
>> new3 = (1+2+3+4+5+6+7, 8)
>>
>>
>> How could I make the above vectors using R?
>>
>>
>> Any suggestion will be greatly appreciated.
>>
>> Best,
>>
>> Kathryn Lord
>>
>>         [[alternative HTML version deleted]]
>>
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