WRT: Say length(V1) is n, do you want to compare > v1[1] with v2[1] and v2[2] and v1[2] with v2[3] and v2[4] > or > v1[1] with v2[1] and v2[n+1] and v1[2] with v2[2] and v2[n+2]
v1[1] with (v2[1] and v2[2]) v1[2] with (v2[3] and v2[4]) v1[3] with (v2[5] and v2[6]) .... ... v1[n] with (v2[n+1] and v2[n+2]) I hope this is clear (I think I was wrong in the snippet of code earlier). Thanks in advance. --MyC > > > My Coyne wrote: >> Hello, >> >> >> >> Newbie question and hope you can help . >> >> I have two vector V1 and V2, where length(V2) = length of (V1) * 2; >> length(V1) ~ 16,000. >> >> For each member in V1, I need to compare 2 element of V2 for equality > > > If just the comparison is concerned, you can do it in vectorized form, > but I am not sure of you want to comapre v1[i] with v2[i] and v2[i+1], > otherwise it would not make sense that length(V2) = length of (V1) * 2 > ... > > Say length(V1) is n, do you want to compare > > v1[1] with v2[1] and v2[2] and v1[2] with v2[3] and v2[4] > or > v1[1] with v2[1] and v2[n+1] and v1[2] with v2[2] and v2[n+2] > > ??? > > Uwe Ligges > > > > > > >> >> >> i.e. >> >> for (I in 1:length (V1)) { >> >> if ( v2[i] == v1[i] & v2[i+1]==v1[i] ){ >> >> statement_1 >> >> statement_2 >> >> . >> >> } >> >> } >> >> >> >> This for-loop is too slow (it takes a good 5 minutes on my Windows >> machine) >> to finish processing the vector V1 of 16,000; I will need to process a >> lot >> more than 16,000 (about 300*16,000). >> >> >> >> Is there a better way to do looping with R? Any help is greatly >> appreciate >> >> >> >> --MyC. >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> >> [[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.