R help - Feb 2009 - Multiple merge, better solution?

Hello,

My problem is that I would like to merge multiple files with a common
column but merge accepts only two
data.frames to merge. In the real situation, I have 26 different
data.frames with a common column. I can of course use merge many times
(see below) but what would be more sophisticated solution? For loop?
Any ideas?

DF1 <- data.frame(var1 = letters[1:5], a = rnorm(5))
DF2 <- data.frame(var1 = letters[3:7], b = rnorm(5))
DF3 <- data.frame(var1 = letters[6:10], c = rnorm(5))
DF4 <- data.frame(var1 = letters[8:12], d = rnorm(5))

g <- merge(DF1, DF2, by.x="var1", by.y="var1", all=T)
g <- merge(g, DF3, by.x="var1", by.y="var1", all=T)
merge(g, DF4, by.x="var1", by.y="var1", all=T)

Thanks in advance.

-Lauri

Hi: Below is a TOTAL HACK and I don't recommend it but it does seem to 
do what you want. I think that I remember Gabor saying that you can 
merge multiple data frames using zoo but I don't know the specifics. I'm
sure he'll respond with the correct way. Below uses a global variable 
to access the
dataframe inside the loop and keeps adding on to it. Don't use it unless 
you're really desperate for a solution.

DF <- DF1

for ( .df in list(DF2,DF3,DF4) ) {
   DF<<-merge(DF,.df,by.x="var1", by.y="var1", all=T)
}

print(DF)



On Thu, Feb 19, 2009 at  5:21 AM, Lauri Nikkinen wrote:
> Hello,
>
> My problem is that I would like to merge multiple files with a common
> column but merge accepts only two
> data.frames to merge. In the real situation, I have 26 different
> data.frames with a common column. I can of course use merge many times
> (see below) but what would be more sophisticated solution? For loop?
> Any ideas?
>
> DF1 <- data.frame(var1 = letters[1:5], a = rnorm(5))
> DF2 <- data.frame(var1 = letters[3:7], b = rnorm(5))
> DF3 <- data.frame(var1 = letters[6:10], c = rnorm(5))
> DF4 <- data.frame(var1 = letters[8:12], d = rnorm(5))
>
> g <- merge(DF1, DF2, by.x="var1", by.y="var1",
all=T)
> g <- merge(g, DF3, by.x="var1", by.y="var1", all=T)
> merge(g, DF4, by.x="var1", by.y="var1", all=T)
>
> Thanks in advance.
>
> -Lauri
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Hi,


I think Reduce could help you.

DF1 <- data.frame(var1 = letters[1:5], a = rnorm(5))
DF2 <- data.frame(var1 = letters[3:7], b = rnorm(5))
DF3 <- data.frame(var1 = letters[6:10], c = rnorm(5))
DF4 <- data.frame(var1 = letters[8:12], d = rnorm(5))

g <- merge(DF1, DF2, by.x="var1", by.y="var1", all=T)
g <- merge(g, DF3, by.x="var1", by.y="var1", all=T)
g <- merge(g, DF4, by.x="var1", by.y="var1", all=T)

test <- Reduce(function(x, y) merge(x, y, all=T,by.x="var1",  
by.y="var1"),
			list(DF1, DF2, DF3, DF4), accumulate=F)

all.equal(test, g) # TRUE


As a warning, it's the first time I've ever used it myself...


Hope this helps,

baptiste



On 19 Feb 2009, at 10:21, Lauri Nikkinen wrote:
> Hello,
>
> My problem is that I would like to merge multiple files with a common
> column but merge accepts only two
> data.frames to merge. In the real situation, I have 26 different
> data.frames with a common column. I can of course use merge many times
> (see below) but what would be more sophisticated solution? For loop?
> Any ideas?
>
> DF1 <- data.frame(var1 = letters[1:5], a = rnorm(5))
> DF2 <- data.frame(var1 = letters[3:7], b = rnorm(5))
> DF3 <- data.frame(var1 = letters[6:10], c = rnorm(5))
> DF4 <- data.frame(var1 = letters[8:12], d = rnorm(5))
>
> g <- merge(DF1, DF2, by.x="var1", by.y="var1",
all=T)
> g <- merge(g, DF3, by.x="var1", by.y="var1", all=T)
> merge(g, DF4, by.x="var1", by.y="var1", all=T)
>
> Thanks in advance.
>
> -Lauri
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
_____________________________

Baptiste Augui?

School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK

Phone: +44 1392 264187

http://newton.ex.ac.uk/research/emag

Another option using Recall,


merge.rec <- function(.list, ...){
	if(length(.list)==1) return(.list[[1]])
	Recall(c(list(merge(.list[[1]], .list[[2]], ...)), .list[-(1:2)]), ...)
}

my.list <- list(DF1, DF2, DF3, DF4)
test2 <- merge.rec(my.list, by.x="var1", by.y="var1",
all=T)

all.equal(test2, g)

Note that your second example does not work because in the last step  
there are no common names between g and DF4 (I think). Using  
suffixes=c("", "") seems to do the trick but I'm not
sure it's giving
the result you want/expect.

Hope this helps,

baptiste



On 19 Feb 2009, at 10:21, Lauri Nikkinen wrote:
> Hello,
>
> My problem is that I would like to merge multiple files with a common
> column but merge accepts only two
> data.frames to merge. In the real situation, I have 26 different
> data.frames with a common column. I can of course use merge many times
> (see below) but what would be more sophisticated solution? For loop?
> Any ideas?
>
> DF1 <- data.frame(var1 = letters[1:5], a = rnorm(5))
> DF2 <- data.frame(var1 = letters[3:7], b = rnorm(5))
> DF3 <- data.frame(var1 = letters[6:10], c = rnorm(5))
> DF4 <- data.frame(var1 = letters[8:12], d = rnorm(5))
>
> g <- merge(DF1, DF2, by.x="var1", by.y="var1",
all=T)
> g <- merge(g, DF3, by.x="var1", by.y="var1", all=T)
> merge(g, DF4, by.x="var1", by.y="var1", all=T)
>
> Thanks in advance.
>
> -Lauri
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
_____________________________

Baptiste Augui?

School of Physics
University of Exeter
Stocker Road,
Exeter, Devon,
EX4 4QL, UK

Phone: +44 1392 264187

http://newton.ex.ac.uk/research/emag