[R] How to replace a column in a data frame with another one with a different size

[arun]

Hi,

As the error says, the replacements should have equal number of rows.
You can either do it adding NAs,
df$V1<-c(NA,rollapply(df$V1,3,mean),NA)
df
   V1
1  NA
2   2
3   3
4   4
5   5
6   6
7   7
8   8
9   9
10 NA
#or,
#use any of these
#as Michael suggested
df2<-rollapply(df,3,mean,fill=NA)

df3<-rollapply(df,3,mean,na.pad=TRUE)
identical(df2,df3)
[1] TRUE

A.K.



----- Original Message -----
From: Stathis Kamperis <ekamperi at gmail.com>
To: r-help at r-project.org
Cc: 
Sent: Sunday, July 8, 2012 10:31 AM
Subject: [R] How to replace a column in a data frame with another one with a different size

Hello everyone,

I have a dataframe with 1 column and I'd like to replace that column
with a moving average.
Example:

> library('zoo')
> mydat <- seq_len(10)
> mydat
[1]  1  2  3  4  5  6  7  8  9 10
> df <- data.frame("V1" = mydat)
> df
   V1
1   1
2   2
3   3
4   4
5   5
6   6
7   7
8   8
9   9
10 10



> df[df$V1 <- rollapply(df$V1, 3, mean)]
Error in `$<-.data.frame`(`*tmp*`, "V1", value = c(2, 3, 4, 5, 6, 7, 8,  :
  replacement has 8 rows, data has 10
>

I could use a temporary variable to store the results of rollapply()
and then reconstruct the data frame, but I was wondering if there is a
one-liner that can achieve the same thing.

Best regards,
Stathis

P.S. If you don't mind, cc me at your reply because I'm not subscribed
to the list (but I will check the archive anyway).

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