[R] Multiple merge, better solution?

[Lauri Nikkinen]

That's perfectly fine. I figured out how to to this with my second example

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

DF <- DF1
for ( .df in list(DF2,DF3,DF4) ) {
     DF <-merge(DF,.df,by.x="var1", by.y="var1", all=T)
     names(DF)[-1] <- paste(names(DF)[-1], 2:length(names(DF)))
}
names(DF) <- sub("[[:space:]].+$", "", names(DF), perl=T)
DF

Thank you all!

-Lauri
2009/2/19 baptiste auguie <ba208 at exeter.ac.uk>:
> If you don't mind I've added this example to the R wiki,
>
> http://wiki.r-project.org/rwiki/doku.php?id=tips:data-frames:merge
>
> It would be very nice if a R guru could check that the information I put is
> not complete fantasy. Feel free to remove as appropriate.
>
> Best wishes,
>
> baptiste
>
>
> On 19 Feb 2009, at 11:00, Lauri Nikkinen wrote:
>
>> Thanks, both solutions work fine. I tried these solutions to my real
>> data, and I got an error
>>
>> Error in match.names(clabs, names(xi)) :
>>  names do not match previous names
>>
>> I refined this example data to look more like my real data, this also
>> produces the same error. Any ideas how to prevent this error?
>>
>> DF1 <- data.frame(var1 = letters[1:5], a = rnorm(5), b = rnorm(5), c =
>> rnorm(5))
>> DF2 <- data.frame(var1 = letters[3:7], a = rnorm(5), b = rnorm(5), c =
>> rnorm(5))
>> DF3 <- data.frame(var1 = letters[6:10], a = rnorm(5), b = rnorm(5), c
>> = rnorm(5))
>> DF4 <- data.frame(var1 = letters[8:12], a = rnorm(5), b = rnorm(5), c
>> = 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)
>>
>> Error in match.names(clabs, names(xi)) :
>>  names do not match previous names
>>
>>> DF <- DF1
>>> for ( .df in list(DF2,DF3,DF4) ) {
>>
>> +  DF <-merge(DF,.df,by.x="var1", by.y="var1", all=T)
>> + }
>>
>> Error in match.names(clabs, names(xi)) :
>>  names do not match previous names
>>
>>> Reduce(function(x, y) merge(x, y, all=T,by.x="var1", by.y="var1"),
>>> list(DF1, DF2, DF3, DF4), accumulate=F)
>>
>> Error in match.names(clabs, names(xi)) :
>>  names do not match previous names
>>
>> - Lauri
>>
>> 2009/2/19 baptiste auguie <ba208 at exeter.ac.uk>:
>>>
>>> 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 Auguié
>>>
>>> School of Physics
>>> University of Exeter
>>> Stocker Road,
>>> Exeter, Devon,
>>> EX4 4QL, UK
>>>
>>> Phone: +44 1392 264187
>>>
>>> http://newton.ex.ac.uk/research/emag
>>> ______________________________
>>>
>>>
>
> _____________________________
>
> Baptiste Auguié
>
> School of Physics
> University of Exeter
> Stocker Road,
> Exeter, Devon,
> EX4 4QL, UK
>
> Phone: +44 1392 264187
>
> http://newton.ex.ac.uk/research/emag
> ______________________________
>
>