[R] Need help on dataframe

[John Kane]

Well, a rather simple-minded, brute force approach would be to add a factor variable to the data frame and use aggregate on it.

I am sure there are better ways but this will work.

EXAMPLE
###
xx  <-  data.frame(aa =1:24, 
                     b = matrix(sample(c(1,2,3,4,5,6), 72,  replace = TRUE), nrow= 24))
  dd  <-rep(c("a","b"), each= 12)
  
  xx  <-  cbind(dd, xx)
  
  aggregate(xx[,3:5], list(xx$dd), mean)

################

By the way, when supplying data samples a good way is to use the dput command. Try ?dput for information
John Kane
Kingston ON Canada


> -----Original Message-----
> From: simolas2008 at gmail.com
> Sent: Sat, 5 Jan 2013 15:33:03 +0200
> To: r-help at r-project.org
> Subject: [R] Need help on dataframe
> 
> Dear R users, I came up to a problem by taking means (or other summary
> statistics) of a big dataframe.
> 
> Suppose we do have a dataframe:
> 
> ID  V1  V2  V3  V4 ........................ V71
>  1    6     5    3     2  ........................  3
>  2    3     2    2     1  ........................  1
>  3    6     5    3     2  ........................  3
>  4    12   15  3     2  ........................  100
> ........................................................
> ........................................................
> 288 10  20  30   30 .......................... 499
> 
> I need to find out the way, how to calculate a mean of every 12 lines to
> get:
> 
> V1                              V2                V3                 V4
> ........................... V71
> mean from 1 to 7       same as V1    same as V1
> mean from 8 to 14     same as V1    same as V1
> etc.
> 
> I can do it column by column using:
> 
> y.ts <- ts(y$V1, frequency=12)
> aggregate(y.ts, FUN=mean)
> 
> Bu this is a hardcore... Can anyone suggest a better way to compute all
> the
> dataframe at once and get a result as matrix?
> 
> Thank you in advance!
> 
> --
> Simonas Kecorius
> **
> 
> 	[[alternative HTML version deleted]]
> 
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