Hi, May be this helps: set.seed(24) B101<- data.frame(SID=sample(400:450,20,replace=FALSE),zGRADE=sample(0:10,20,replace=TRUE),col3=rnorm(20)) set.seed(28) B2A<- data.frame(SID=sample(400:600,50,replace=FALSE),zGRADE=sample(0:10,50,replace=TRUE),col3=rnorm(50)) set.seed(35) B2B<- data.frame(SID=sample(400:600,50,replace=FALSE),zGRADE=sample(0:10,50,replace=TRUE),col3=rnorm(50)) set.seed(45) B2C<- data.frame(SID=sample(400:600,120,replace=FALSE),zGRADE=sample(0:10,120,replace=TRUE),col3=rnorm(120)) Master<- data.frame(SID=400:600) library(plyr) Master1<-join_all(list(Master,B101[,1:2],B2A[,1:2],B2B[,1:2],B2C[,1:2]),by="SID") colnames(Master1)[-1]<- c("B101","B2A","B2B","B2C")
head(Master1,3) # SID B101 B2A B2B B2C #1 400 NA 8 NA 3 #2 401 6 NA NA 9 #3 402 NA NA 5 NA tail(Master1,3) # SID B101 B2A B2B B2C #199 598 NA NA NA NA #200 599 NA NA NA 8 #201 600 NA 2 NA 4 A.K. ----- Original Message ----- From: Robert Lynch <robert.b.ly...@gmail.com> To: r-help@r-project.org Cc: Sent: Tuesday, June 18, 2013 8:16 PM Subject: [R] data selection I have two different data frames ( actually a set of data frames for each class and one master one into which i want pull some data from each of the frame in the set) one is all students that have taken a course so the set of data frames is B101 B2A B2B B2C etc. . . and each one has lots of data e.g. B101 SID zGRADE 444 -.2 458 0 587 .2 etc and Master SID 587 etc and I would like to make a field in master for each data frame e.g. Master$B101, Master$B2A and populate it with the zGrades from each of the data frames the SID in Master are a wholely containted sub set of the ones in each of the other data frames [[alternative HTML version deleted]] ______________________________________________ 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.