[R] data frames; matching/merging
Hi all, I'm feeling a little guilty to ask this question, since I've written a solution using a rather clunky for loop that gets the job done. But I'm convinced there must be a faster (and probably more elegant) way to accomplish what I'm looking to do (perhaps using the merge function?). I figured somebody out there might've already figured this out: I have a dataframe with two columns (let's call them V1 and V2). All rows are unique, although column V1 has several redundant entries. Ex: V1 V2 1a3 2a2 3b9 4c4 5a7 6b11 What I'd like is to return a dataframe cut down to have only unique entires in V1. V2 should contain a vector, for each V1, that is the minimum of all the possible choices from the set of redundant V1's. Example output: V1 V2 1 a2 2 b9 3 c4 If somebody could (relatively easily) figure out how to get closer to a solution, I'd appreciate hearing how. Also, I'd be interested to hear how you came upon the answer (so I can get better at searching the R resources myself). Regards, Jonathan __ R-help@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.
Re: [R] data frames; matching/merging
On Mon, Feb 8, 2010 at 11:39 AM, Jonathan jonsle...@gmail.com wrote: Hi all, I'm feeling a little guilty to ask this question, since I've written a solution using a rather clunky for loop that gets the job done. But I'm convinced there must be a faster (and probably more elegant) way to accomplish what I'm looking to do (perhaps using the merge function?). I figured somebody out there might've already figured this out: I have a dataframe with two columns (let's call them V1 and V2). All rows are unique, although column V1 has several redundant entries. Ex: V1 V2 1 a 3 2 a 2 3 b 9 4 c 4 5 a 7 6 b 11 What I'd like is to return a dataframe cut down to have only unique entires in V1. V2 should contain a vector, for each V1, that is the minimum of all the possible choices from the set of redundant V1's. Example output: V1 V2 1 a 2 2 b 9 3 c 4 If somebody could (relatively easily) figure out how to get closer to a solution, I'd appreciate hearing how. Also, I'd be interested to hear how you came upon the answer (so I can get better at searching the R resources myself). Regards, Jonathan __ R-help@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. -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem that you are trying to solve? __ R-help@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.
Re: [R] data frames; matching/merging
Hi! I'm definitely not an expert in R (and it's my first reply!), but if I understand right, I think the aggregate function might do what you're looking for. Try ?aggregate to get more info. You might find what you need! HTH Ivan Le 2/8/2010 17:39, Jonathan a écrit : Hi all, I'm feeling a little guilty to ask this question, since I've written a solution using a rather clunky for loop that gets the job done. But I'm convinced there must be a faster (and probably more elegant) way to accomplish what I'm looking to do (perhaps using the merge function?). I figured somebody out there might've already figured this out: I have a dataframe with two columns (let's call them V1 and V2). All rows are unique, although column V1 has several redundant entries. Ex: V1 V2 1a3 2a2 3b9 4c4 5a7 6b11 What I'd like is to return a dataframe cut down to have only unique entires in V1. V2 should contain a vector, for each V1, that is the minimum of all the possible choices from the set of redundant V1's. Example output: V1 V2 1 a2 2 b9 3 c4 If somebody could (relatively easily) figure out how to get closer to a solution, I'd appreciate hearing how. Also, I'd be interested to hear how you came upon the answer (so I can get better at searching the R resources myself). Regards, Jonathan __ R-help@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. __ R-help@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.
Re: [R] data frames; matching/merging
x - read.table(textConnection(V1 V2 + 1a3 + 2a2 + 3b9 + 4c4 + 5a7 + 6b11), header=TRUE) closeAllConnections() # close; matrix with rownames - easy enough to change into a dataframe if you want cbind(tapply(x$V2, x$V1, min)) [,1] a2 b9 c4 On Mon, Feb 8, 2010 at 11:39 AM, Jonathan jonsle...@gmail.com wrote: Hi all, I'm feeling a little guilty to ask this question, since I've written a solution using a rather clunky for loop that gets the job done. But I'm convinced there must be a faster (and probably more elegant) way to accomplish what I'm looking to do (perhaps using the merge function?). I figured somebody out there might've already figured this out: I have a dataframe with two columns (let's call them V1 and V2). All rows are unique, although column V1 has several redundant entries. Ex: V1 V2 1 a 3 2 a 2 3 b 9 4 c 4 5 a 7 6 b 11 What I'd like is to return a dataframe cut down to have only unique entires in V1. V2 should contain a vector, for each V1, that is the minimum of all the possible choices from the set of redundant V1's. Example output: V1 V2 1 a 2 2 b 9 3 c 4 If somebody could (relatively easily) figure out how to get closer to a solution, I'd appreciate hearing how. Also, I'd be interested to hear how you came upon the answer (so I can get better at searching the R resources myself). Regards, Jonathan __ R-help@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. -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem that you are trying to solve? __ R-help@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.
Re: [R] data frames; matching/merging
On Feb 8, 2010, at 11:39 AM, Jonathan wrote:
Hi all,
I'm feeling a little guilty to ask this question, since I've
written a solution using a rather clunky for loop that gets the job
done. But I'm convinced there must be a faster (and probably more
elegant) way to accomplish what I'm looking to do (perhaps using the
merge function?). I figured somebody out there might've already
figured this out:
I have a dataframe with two columns (let's call them V1 and V2). All
rows are unique, although column V1 has several redundant entries.
Ex:
V1 V2
1a3
2a2
3b9
4c4
5a7
6b11
What I'd like is to return a dataframe cut down to have only unique
entires in V1. V2 should contain a vector, for each V1, that is the
minimum of all the possible choices from the set of redundant V1's.
rd.txt
function(txt, header=TRUE,...) {
rd-read.table(textConnection(txt), header=header, ...)
closeAllConnections()
rd}
DF - rd.txt(V1 V2
+ 1a3
+ 2a2
+ 3b9
+ 4c4
+ 5a7
+ 6b11
+ )
tapply(DF$V2, DF$V1, min)
a b c
2 9 4
as.data.frame.table(tapply(DF$V2, DF$V1, min))
Var1 Freq
1a2
2b9
3c4
DF2 - as.data.frame.table(tapply(DF$V2, DF$V1, min))
names(DF2) - names(DF)
DF2
V1 V2
1 a 2
2 b 9
3 c 4
Example output:
V1 V2
1 a2
2 b9
3 c4
If somebody could (relatively easily) figure out how to get closer to
a solution, I'd appreciate hearing how. Also, I'd be interested to
hear how you came upon the answer (so I can get better at searching
the R resources myself).
Regards,
Jonathan
__
R-help@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.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
__
R-help@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.
Re: [R] data frames; matching/merging
You could try aggregate:
If we call your data frame df:
aggregate(df[2], by=df[1], FUN=min)
will get you what you asked for (if not necessarily what you need ;-)
)
Switching the columns around is easy enough if you need to; proceeding
stepwise:
df.new-aggregate(df[2], by=df[1], FUN=min)
df.new[,c(2,1)]
As to how I found aggregate: watching R-help daily for years
occasionally pops up fundamental gems like aggregate...
Steve Ellison
LGC
Jonathan jonsle...@gmail.com 08/02/2010 16:39:11
What I'd like is to return a dataframe cut down to have only unique
entires in V1. V2 should contain a vector, for each V1, that is the
minimum of all the possible choices from the set of redundant V1's.
Example output:
V1 V2
1 a2
2 b9
3 c4
***
This email and any attachments are confidential. Any use...{{dropped:8}}
__
R-help@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.
Re: [R] data frames; matching/merging
Here are 3 solutions assuming DF contains the data frame: # 1. aggregate aggregate(DF[2], DF[1], min) V1 V2 1 a 2 2 b 9 3 c 4 # 2. aggregate.formula - requires R 2.11.x aggregate(V2 ~ V1, DF, min) V1 V2 1 a 2 2 b 9 3 c 4 # 3. SQL using sqldf library(sqldf) sqldf(select V1, min(V2) V2 from DF group by V1) V1 V2 1 a 2 2 b 9 3 c 4 # 4. summaryBy in the doBy package library(doBy) summaryBy(V2 ~., DF, FUN = min, keep.names = TRUE) V1 V2 1 a 2 2 b 9 3 c 4 On Mon, Feb 8, 2010 at 11:39 AM, Jonathan jonsle...@gmail.com wrote: Hi all, I'm feeling a little guilty to ask this question, since I've written a solution using a rather clunky for loop that gets the job done. But I'm convinced there must be a faster (and probably more elegant) way to accomplish what I'm looking to do (perhaps using the merge function?). I figured somebody out there might've already figured this out: I have a dataframe with two columns (let's call them V1 and V2). All rows are unique, although column V1 has several redundant entries. Ex: V1 V2 1 a 3 2 a 2 3 b 9 4 c 4 5 a 7 6 b 11 What I'd like is to return a dataframe cut down to have only unique entires in V1. V2 should contain a vector, for each V1, that is the minimum of all the possible choices from the set of redundant V1's. Example output: V1 V2 1 a 2 2 b 9 3 c 4 If somebody could (relatively easily) figure out how to get closer to a solution, I'd appreciate hearing how. Also, I'd be interested to hear how you came upon the answer (so I can get better at searching the R resources myself). Regards, Jonathan __ R-help@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. __ R-help@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.
