[R] Identifying records with the correct number of repeated measures

[Keith Larson]

Dear list,

I have a dataset where we sampled multiple individuals either 1 or 9
times. Our measurement variable is 'Delta13C' (see below sample
dataset). I cannot figure out how to efficiently use a vector command
(preferably) or a loop to create a new vector of the names of the
individuals sampled 9 times. Note that the 'FeatherPosition' variable
will only be "P1" for individuals sampled only once, while it will be
%in% c('P1', 'P2', 'P3', 'P4', 'P5', 'P6', 'P7', 'P8', 'P9')  for
individuals sampled 9 times. In my sample data below the new vector
(e.g. WW_Names) would include only 'WW_08I_01' and 'WW_08I_03'.

Two other quick questions: 1) how can I re-number my 'ROWID', as when
I subset my complete dataset to a smaller dataset the old ROWID's are
no longer meaningful, and 2) when I subset my dataset my 'factor'
variables contain all the levels from the complete dataset, how can I
reset these factor variables to condense my 'dump' file as much as
possible?

Many Holiday Cheers from a NEW R user!
Keith

Sample data:

WW_Sample_SI <-
structure(list(Individual_ID = structure(c(1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 4L, 5L
), .Label = c("WW_08I_01", "WW_08I_02", "WW_08I_03", "WW_08I_04",
"WW_08I_05"), class = "factor"), Site_Name = structure(c(1L,
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 1L, 1L), .Label = "Anjan", class = "factor"), Latitude = c(63.72935,
63.72935, 63.72935, 63.72935, 63.72935, 63.72935, 63.72935, 63.72935,
63.72935, 63.72935, 63.72935, 63.72935, 63.72935, 63.72935, 63.72935,
63.72935, 63.72935, 63.72935, 63.72935, 63.72935, 63.72935),
    Longitude = c(12.54022, 12.54022, 12.54022, 12.54022, 12.54022,
    12.54022, 12.54022, 12.54022, 12.54022, 12.54022, 12.54022,
    12.54022, 12.54022, 12.54022, 12.54022, 12.54022, 12.54022,
    12.54022, 12.54022, 12.54022, 12.54022), FeatherPosition = structure(c(1L,
    2L, 3L, 4L, 5L, 6L, 7L, 8L, 9L, 1L, 1L, 2L, 3L, 4L, 5L, 6L,
    7L, 8L, 9L, 1L, 1L), .Label = c("P1", "P2", "P3", "P4", "P5",
    "P6", "P7", "P8", "P9"), class = "factor"), Delta13C = c(-18.3,
    -18.53, -19.55, -20.18, -20.96, -21.08, -21.5, -17.42, -13.18,
    -19.95, -22.3, -22.2, -22.18, -22.14, -21.55, -20.85, -23.1,
    -20.75, -20.9, -21.61, -22.24)), .Names = c("Individual_ID",
"Site_Name", "Latitude", "Longitude", "FeatherPosition", "Delta13C"
), class = "data.frame", row.names = c("1282", "1277", "1279",
"1270", "1272", "1274", "1280", "1276", "1271", "1284", "1289",
"1290", "1295", "1293", "1292", "1288", "1291", "1285", "1297",
"1298", "1299"))

*******************************************************************************************
Keith Larson, PhD Student
Evolutionary Ecology, Lund University
Sölvegatan 37
223 62 Lund Sweden
Phone: +46 (0)46 2229014 Mobile: +46 (0)73 0465016 Fax: +46 (0)46 2224716
Skype: sternacaspia FB: keith.w.larson at gmail.com