[R] data manipulation: getting mean value every 5 rows

[Spencer Graves]

Have you considered "aggregate" [documented in help(aggregate) or 
"www.r-project.org" -> search -> "R site search" or Venables and Ripley, 
Modern Applied Statistics with S]?

hope this helps.  spencer graves

Federico Calboli wrote:
> Dear All,
> 
> I would like to ask you how to accomplish a little tricky data
> manipulation. I have a large dataset, looking something like:
> 
> temp	line	cage	number
> 18	18	1	6678.63
> 18	18	1	7774.458
> 18	18	1	7845.902
> 18	18	1	9483.578
> 18	18	1	8983.555
> 18	18	1	9181.052
> 18	18	1	9458.696
> 18	18	1	8138.616
> 18	18	1	7981.994
> 18	18	1	7556.491
> 18	18	1	7672.137
> 18	18	1	6607.776
> 18	18	1	8383.65
> 18	18	1	7129.852
> 18	18	1	8536.667
> 18	18	2	8287.8
> 18	18	2	7924.47
> 18	18	2	7928.474
> 18	18	2	7363.157
> 18	18	2	7952.593
> .....
> 
> I would like to create a dataframe where I get the mean values, 5 rows at a
> time, of columns "number", while keeping the value in the other columns
> fixed to the vaules found in the first of the 5 rows (or whatever, it's the
> same for the 5 rows) so that the above would be "shrunk" to:
> 
> temp	line	cage	number	
> 18	18	1	8153.2246
> 18	18	1	8463.3698
> 18	18	1	7666.0164
> 18	18	2	7891.2988
>  
> Any hints?
> 
> Regards,
> 
> Federico Calboli
> 
> =========================
> 
> Federico C.F. Calboli
> 
> Department of Biology
> University College London
> Room 327
> Darwin Building
> Gower Street
> London
> WClE 6BT
> 
> Tel: (+44) 020 7679 4395 
> Fax (+44) 020 7679 7096
> f.calboli at ucl.ac.uk
> 
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