[R] merging several dataframes from a list

[Phil Spector]

Another possibility is Reduce:

> Reduce(function(x,y,by='pos')merge(x,y,by='pos'),mylist)
   pos data.x data.y data
1   A      2      6    9
2   B      6      2    3
3   C      3      9    6
4   D      1      7    2
5   E      9      5    1

                                        - Phil Spector
 					 Statistical Computing Facility
 					 Department of Statistics
 					 UC Berkeley
 					 spector at stat.berkeley.edu



On Wed, 21 Jan 2009, Antje wrote:

> Hi there,
>
> I have a list of dataframes (generated by reading multiple files) and all 
> dataframes are comparable in dimension and column names. They also have a 
> common column, which, I'd like to use for merging. To give a simple example 
> of what I have:
>
> df1 <- data.frame(c(LETTERS[1:5]), c(2,6,3,1,9))
> names(df1) <- c("pos", "data")
> df3 <- df2 <- df1
> df2$data <- c(6,2,9,7,5)
> df3$data <- c(9,3,6,2,1)
> mylist <- list(df1,df2,df3)
> names(mylist) <- c("df1","df2","df3")
>
>> mylist
>
> $df1
>  pos data
> 1   A    2
> 2   B    6
> 3   C    3
> 4   D    1
> 5   E    9
>
> $df2
>  pos data
> 1   A    6
> 2   B    2
> 3   C    9
> 4   D    7
> 5   E    5
>
> $df3
>  pos data
> 1   A    9
> 2   B    3
> 3   C    6
> 4   D    2
> 5   E    1
>
> If I use do.call("cbind"), I'll end up with something like this
>
>   pos data pos data pos data
> 1   A    2   A    6   A    9
> 2   B    6   B    2   B    3
> 3   C    3   C    9   C    6
> 4   D    1   D    7   D    2
> 5   E    9   E    5   E    1
>
>
> but now, I don't know anymore which data comes from which dataframe... and I 
> have the column "pos" multiple times...
>
> Instead I'd like to have it like this:
>
>   pos df1 df2 df3
> 1   A    2   6   9
> 2   B    6   2   3
> 3   C    3   9   6
> 4   D    1   7   2
> 5   E    9   5   1
>
> How, can I realize it? (The list, I'm working with has not just 3 data frames 
> like given in my example, so I need to automize it)
>
>
> Antje
>
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