Thanks Petr! It is good to see multiple solutions to the same problem. Best,
Jude -----Original Message----- From: Petr PIKAL [mailto:petr.pi...@precheza.cz] Sent: Wednesday, September 23, 2009 10:59 AM To: Ryan, Jude Cc: alxmil...@yahoo.it; r-help@r-project.org Subject: Re: [R] compute differences Hi You can use outer. If your data are in data frame test then DIFF <- as.vector(t(outer(test$val, test$val, "-"))) returns a vector, You just need to add suitable names to rows. CASE <- as.vector(t(outer(test$ID, test$ID, paste, sep="-"))) data.frame(CASE, DIFF) will put it together. Regards Petr r-help-boun...@r-project.org napsal dne 23.09.2009 16:42:45: > Alessandro Carletti wrote: > > > > Hi, > > I have a problem. > > I have a data frame looking like: > > > > ID val > > > > A? .3 > > B? 1.2 > > C? 3.4 > > D? 2.2 > > E? 2.0 > > > > I need to CREATE the following TABLE: > > > > CASE?? DIFF > > > > A-A??? 0 > > A-B??? -0.9 > > A-C??? -3.1 > > A-D??? -1.9 > > A-E??? -1.7 > > B-A??? ... > > B-B??? ... > > B-C > > B-D > > B-E > > C-A > > ... > > > > WHERE CASE IS THE COUPLE OF ELEMENTS CONSIDEREDM AND DIFF IS THE > computed DIFFERENCE between their values. > > > > Could you give me suggestions? > > > > Solution: > > Besides the suggestions given by others, you can use the sqldf package > to do this (leveraging knowledge in SQL if you know SQL). If you join > your data frame with itself, without a join condition, you will get the > Cartesian product of the two data frames, which seems to be exactly what > you need. A warning is in order. Generally when you join 2 (or more) > data frames you DO NOT want the Cartesian product by want to join the > data frames by some key. The solution to your particular problem, > however, can be implemented easily using the Cartesian product. > > > > mydata <- data.frame(id=rep(c('A','B','C','D','E'), each=2), > val=sample(1:5, 10, replace=T)) > > mydata > > library(sqldf) > > # merge data frame with itself to create a Cartesian Product - this is > normally NOT what you want. > > # Note 'case' is a key word in SQL so I use cases for the variable name. > Likewise diff is a used in R so I use diffr > > mydata2 <- sqldf("select a.id as id1, a.val as val1, b.id as id2, b.val > as val2, a.id || ' - ' || b.id as cases, > > a.val - b.val as diffr from mydata a, mydata b") > > dim(mydata2) # check dimensions of the merged dataset > > head(mydata2) # examine the first 6 records > > # if you want only the columns casses and diffr, then use this SQL code > > mydata3 <- sqldf("select a.id || ' - ' || b.id as cases, a.val - b.val > as diffr from mydata a, mydata b") > > dim(mydata3) # check dimensions of the merged dataset > > head(mydata3) # examine the first 6 records > > > > Hope this helps. > > > > Jude > > ___________________________________________ > Jude Ryan > Director, Client Analytical Services > Strategy & Business Development > UBS Financial Services Inc. > 1200 Harbor Boulevard, 4th Floor > Weehawken, NJ 07086-6791 > Tel. 201-352-1935 > Fax 201-272-2914 > Email: jude.r...@ubs.com > > > > Please do not transmit orders or instructions regarding a UBS > account electronically, including but not limited to e-mail, > fax, text or instant messaging. The information provided in > this e-mail or any attachments is not an official transaction > confirmation or account statement. For your protection, do not > include account numbers, Social Security numbers, credit card > numbers, passwords or other non-public information in your e-mail. > Because the information contained in this message may be privileged, > confidential, proprietary or otherwise protected from disclosure, > please notify us immediately by replying to this message and > deleting it from your computer if you have received this > communication in error. Thank you. > > UBS Financial Services Inc. > UBS International Inc. > UBS Financial Services Incorporated of Puerto Rico > UBS AG > > > UBS reserves the right to retain all messages. Messages are protected > and accessed only in legally justified > cases.______________________________________________ > 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. Please do not transmit orders or instructions regarding a UBS account electronically, including but not limited to e-mail, fax, text or instant messaging. The information provided in this e-mail or any attachments is not an official transaction confirmation or account statement. For your protection, do not include account numbers, Social Security numbers, credit card numbers, passwords or other non-public information in your e-mail. Because the information contained in this message may be privileged, confidential, proprietary or otherwise protected from disclosure, please notify us immediately by replying to this message and deleting it from your computer if you have received this communication in error. Thank you. UBS Financial Services Inc. UBS International Inc. UBS Financial Services Incorporated of Puerto Rico UBS AG UBS reserves the right to retain all messages. Messages are protected and accessed only in legally justified cases. ______________________________________________ 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.
