# [R] summarise subsets of a vector

Jessica Streicher j.streicher at micromata.de
Wed Jan 23 17:35:51 CET 2013

```Or...

fs<-rep(1:ceiling(length(test)/10),each=10)[1:length(test)]
result<-by(test,fs,mean)

which will get you the version with the 101st as a single datapoint
so many possibilities..

On 23.01.2013, at 16:43, David L Carlson wrote:

> You didn't indicate what you want to do with the 101st observation. Arun's
> solution creates an 11th group and divides by the number in the group(1),
> while Jessica's solution creates an 11th column and divides by 10.
>
>> test[101] <- 100
>> unlist(lapply(split(test,((seq_along(test)-1)%/% 10)+1),mean))
>         1          2          3          4          5          6          7
>
>  0.000000   0.000000   0.000000   0.000000   0.000000   0.000000   0.000000
>
>         8          9         10         11
>  0.146375   0.000000   0.194500 100.000000
>> x<-matrix(test,nrow=10)
> Warning message:
> In matrix(test, nrow = 10) :
>  data length [101] is not a sub-multiple or multiple of the number of rows
> [10]
>> apply(x,2,mean)
> [1]  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000  0.000000
> [8]  0.146375  0.000000  0.194500 10.000000
>
> Another approach would be to use aggregate:
>
>> Groups <- gl(ceiling(length(test)/10), 10)[1:length(test)]
>> aggregate(test, list(Groups), mean)
>   Group.1          x
> 1        1   0.000000
> 2        2   0.000000
> 3        3   0.000000
> 4        4   0.000000
> 5        5   0.000000
> 6        6   0.000000
> 7        7   0.000000
> 8        8   0.146375
> 9        9   0.000000
> 10      10   0.194500
> 11      11 100.000000
>
> ----------------------------------------------
> David L Carlson
> Associate Professor of Anthropology
> Texas A&M University
> College Station, TX 77843-4352
>
>
>> -----Original Message-----
>> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
>> project.org] On Behalf Of Jessica Streicher
>> Sent: Wednesday, January 23, 2013 6:13 AM
>> To: Wim Kreinen
>> Cc: r-help
>> Subject: Re: [R] summarise subsets of a vector
>>
>> Or maybe
>>
>> x<-matrix(test,nrow=10)
>> apply(x,2,mean)
>>
>>
>> On 23.01.2013, at 00:09, Wim Kreinen wrote:
>>
>>> Hello,
>>>
>>> I have vector called test. And now I wish to measure the mean of the
>> first
>>> 10 number, the second 10 numbers etc
>>> How does it work?
>>> Thanks Wim
>>>
>>>> dput (test)
>>> c(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
>>> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
>>> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
>>> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.71, 0.21875, 0, 0.27375, 0.26125,
>>> 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0.84125,
>>> 0.0575, 0.92625, 0.12, 0, 0)
>>>
>>> 	[[alternative HTML version deleted]]
>>>
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