# reduce and intersect question (maybe)? Classic List Threaded 3 messages Open this post in threaded view
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## reduce and intersect question (maybe)?

 Hello All, wonder if you have a suggestion for the following: we have a<-data.frame(ID=c(1,2,3,4,5,6,7),date=as.POSIXct(seq(as.Date('2011-01-01'),as.Date('2011-01-07'),by = 1),format='%m/%d/%Y %H:%M'),z=rnorm(7,1,1)) b<-data.frame(ID=c(1,2,3,11,12,13,14,15),date=as.POSIXct(seq(as.Date('2011-01-01'),as.Date('2011-01-08'),by = 1),format='%m/%d/%Y %H:%M'),z=rnorm(8,1,1)) c<-data.frame(ID=c(1,2,3,4,5,6,7,8,9,10),date=as.POSIXct(c(seq(as.Date('2011-01-01'),as.Date('2011-01-05'),by = 1),seq(as.Date('2011-01-11'),as.Date('2011-01-15'),by = 1)),format='%m/%d/%Y %H:%M'),z=rnorm(10,1,1)) d<-data.frame(ID=c(1,2,3,21,22,23,24,25,26,27,28),date=as.POSIXct(c(as.Date('2011-01-01'),as.Date('2011-11-01'),as.Date('2011-01-03'),seq(as.Date('2011-01-01'),as.Date('2011-01-08'),by = 1)),format='%m/%d/%Y %H:%M'),z=rnorm(11,1,1)) #this function will do the obvious and give the IDs that are in all of the data frames based on the ID column intersect_all <- function(a,b,...){   Reduce(intersect, list(a,b,...)) } intersect_all(a\$ID,b\$ID,c\$ID,d\$ID) #I would like to extend this (or use another function) where the function would give all the rows (ie based on both columns as a condition) that are in all of the data frames, so the result should be as below as these 2 rows are in all of the data frames (the fact that the rows that are common in all data frames ie 1 and 3 in my example are I only set up for the sake of convenience, in reality their row number in each of the data frames may be different) . The value of z is of no particular importance, but once the common rows are identified I would want to subset the data frames to get these results: a[c(1,3),] b[c(1,3),] c[c(1,3),] d[c(1,3),] much appreciate your input, thanks Andras  ______________________________________________ [hidden email] mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.