[R] subsetting

[henrik.parn at bio.ntnu.no]

Dear all,

I have received some data on birds that looks sth like this:

# a unique id for each individual
id <- c(1,1,1,2,2,2,3,3,3,4,4,5,6)

# the year the bird was measured
year <- c(1995, 1996, 1997, 1995, 1996, 1997, 1996, 1997, 1998, 1996, 1997, 1997, 1998)

# the year the bird was hatched
year.hatch <- c(1995, 1995, 1995, 1995, 1995, 1995, 1996, 1996, 1996, 1996, 1996, 1997, 1998)

# the year when the bird reproduced the first time (for simplicity in the dummy data, all birds reproduce the year after it was born)
year.1st.reprod <- year.hatch + 1

# some status (0/1) of an individual
status <- c(1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1)

# the id of the mother
id.mother <- c(NA, NA, NA, NA, NA, NA, 1, 1, 1, 2, 2, 3, 3)

# Status of the mother (0/1)
status.mother <- c(NA, NA, NA, NA, NA, NA, 1, 1, 1, 0, 0, 1, 1)

# a measure of individual
measure <- rnorm(13)

test.data <- data.frame(id, year, year.hatch, year.1st.reprod, status,  id.mother, status.mother, measure)
test.data
--------------------------------

I want to compare measures of individuals that have mothers of different status.

But I need help to make the following subset of individuals:

I want the measures that are taken on individuals the year they are hatched. So for the individuals I compare, I want year==year.hatch.

...and 

I also want that the individuals from which I obtain measurements are offspring from the first reproduction year of their parents.
So for the individuals I compare, I want their /mothers/ to have year==year.1st.reproduction.

Applying my selection criteria on the simple dummy data above, I would end up with the measures from id=3 in 1996, id=4 in 1996 and id=5 in 1997.


Can anyone help me how to perform this subsetting in R?


Thanks a lot in advance!


Henrik



-- 
************************
Henrik Pärn


Department of Biology
Norwegian University of Science and Technology
NO-7491 Trondheim
Norge


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