R help - Mar 2012 - aggregate

Dear all I am having a vector with large length and I would like to ask you if I
can aggregate the values by constant sized windows. For example for the
following vector, I would like to take 30 points until the end
and find their mean.

> myData<-seq(1:100000)
>
> c(mean(myData[1:30]),mean(myData[31:60])) #...and so one until the end
[1] 15.5 45.5

I have searched in the R documentation and I found the aggregate but it seems to
operate on data.frames. It also has this by argument where I tried to set it to
30 but it expects there a list rather than a numeric value.

Could you please help me ?
I would like to thank you in advance for your help

B.R
Alex

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On Wed, Mar 14, 2012 at 07:46:40AM -0700, Alaios wrote:
> Dear all I am having a vector with large length and I would like to ask you
if I can aggregate the values by constant sized windows. For example for the
following vector, I would like to take 30 points until the end
> and find their mean.
> 
> 
> > myData<-seq(1:100000)
> >
> > c(mean(myData[1:30]),mean(myData[31:60])) #...and so one until the end
> [1] 15.5 45.5
Hi.

Try the following.

  myData <- 1:100
  gr <- ceiling((1:length(myData))/30)
  c(tapply(myData, gr, FUN=mean))

     1    2    3    4 
  15.5 45.5 75.5 95.5 

Hope this helps.

Petr Savicky.

Hi
> Dear all I am having a vector with large length and I would like to ask 
> you if I can aggregate the values by constant sized windows. For example 
> for the following vector, I would like to take 30 points until the end
> and find their mean.
> 
> 
> > myData<-seq(1:100000)
> >
> > c(mean(myData[1:30]),mean(myData[31:60])) #...and so one until the end
> [1] 15.5 45.5
> 
> I have searched in the R documentation and I found the aggregate but it 
> seems to operate on data.frames. It also has this by argument where I 
Why do you think so? Aggregate works on any suitable object, e.g. vector.
> tried to set it to 30 but it expects there a list rather than a numeric 
value.
>From help page
by
a list of grouping elements, each as long as the variables in x.

the only thing what aggregate wants is

list(some.vector.with.the.same.length.as.variable.you.want.to.aggregate)

as some categorical data according to what you want to perform the 
function operation.

Regards
Petr
> 
> Could you please help me ?
> I would like to thank you in advance for your help
> 
> B.R
> Alex
> 
>    [[alternative HTML version deleted]]
> 
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