Multiple merge, better solution?
The zoo package has a multi-way merge for zoo objects. Its just do.call(merge, z) where z is a list of zoo objects. In detail: set.seed(1) 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)) # create list of data frames DFs <- list(A = DF1, B = DF2, C = DF3, D = DF4) library(zoo) # convert to list of zoo objects z <- lapply(DFs, function(x) zoo(as.matrix(x[ ,-1, drop = FALSE]), as.character(x[,1]))) # perform merge zz <- do.call(merge, z) # to convert back to data frame DF <- as.data.frame(var1 = time(zz), coredata(zz))
On Thu, Feb 19, 2009 at 6:00 AM, Lauri Nikkinen <lauri.nikkinen at iki.fi> 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
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_____________________________ 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 ______________________________
______________________________________________ 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.