[R] vector extraction

[Jens Hainmueller]

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