My understanding is that you want to extract the dv values for year 1980:
color <- with( Test.dataset2, dv[ year == 1980 ] ) --- Date: Mon, 8 Mar 2004 19:36:45 -0800 From: Jens Hainmueller <[EMAIL PROTECTED]> To: R-Help <[EMAIL PROTECTED]> Subject: [R] vector extraction Hello, I could need some help on this one: >From the data.frame "Test.dataset2" below (TSCS data for 151 "countries.to.map" for "year" 1973-95; each "country.to.map" is described by a unique code), I would like to extract a vector "color" that for each "country.to.map" takes on the value of "dv" (a categorical variable with values 1,2,..4) for a specified "year". Thus, for a specified "year", "color" should have 151 obs - one for each "country.to.map" represented by its respective value of "dv"). I tried this: > color <- dv[country.to.map][(year == 1980)[country.to.map]] but it does not give me what I need. I can't figure out where my error is, however. Thanks, Jens > Test.dataset2[1:40,] country.to.map dv year 1 1936 NA 1973 2 1936 NA 1974 3 1936 NA 1975 4 1936 NA 1976 5 1936 NA 1977 6 1936 NA 1978 7 1936 NA 1979 8 1936 NA 1980 9 1936 NA 1981 10 1936 NA 1982 11 1936 NA 1983 12 1936 NA 1984 13 1936 NA 1985 14 1936 NA 1986 15 1936 NA 1987 16 1936 NA 1988 17 1936 4 1989 18 1936 4 1990 19 1936 4 1991 20 1936 4 1992 21 1936 4 1993 22 1936 4 1994 23 1936 4 1995 24 56 4 1973 25 56 4 1974 26 56 2 1975 27 56 2 1976 28 56 2 1977 29 56 2 1978 30 56 2 1979 31 56 2 1980 32 56 2 1981 33 56 2 1982 34 56 4 1983 35 56 4 1984 36 56 4 1985 37 56 4 1986 38 56 4 1987 39 56 4 1988 40 56 4 1989 ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html