adding a dummy variable...

Hi:

Here's another way to do it with the plyr package, also not terribly
elegant. It assumes that rel.head is a factor in your original data
frame:

str(df)

'data.frame': ? 11 obs. of ?2 variables:
?$ ID ? ? ?: Factor w/ 6 levels "17100","17101",..: 1 1 2 3 4 4 5 5 5 6 ...
?$ rel.head: Factor w/ 3 levels "1","2","3": 1 3 1 1 1 2 1 2 3 1 ...

If this is not the case in your data, then you need to modify the
function f below accordingly. (This is why use of dput() is preferred
when sending example data to R-help, BTW.)

library('plyr')
f <- function(d) {
? ?tvec <- factor(c(1, 3), levels = 1:3) ? # target vector
? ?if(nrow(d) != 2L) {d$dummy <- rep(0, nrow(d)); return(d)}
? ?# If the first if statement is FALSE, then the following code is run:
? ? ? d$dummy <- ifelse(!identical(d[, 2], tvec), 0, 1)
? ? ? d
? }

ddply(df, .(ID), f)

? ? ?ID rel.head dummy
1 ?17100 ? ? ? ?1 ? ? 1
2 ?17100 ? ? ? ?3 ? ? 1
3 ?17101 ? ? ? ?1 ? ? 0
4 ?17102 ? ? ? ?1 ? ? 0
5 ?17103 ? ? ? ?1 ? ? 0
6 ?17103 ? ? ? ?2 ? ? 0
7 ?17104 ? ? ? ?1 ? ? 0
8 ?17104 ? ? ? ?2 ? ? 0
9 ?17104 ? ? ? ?3 ? ? 0
10 17105 ? ? ? ?1 ? ? 1
11 17105 ? ? ? ?3 ? ? 1

HTH,
Dennis

On Tue, Oct 4, 2011 at 8:44 AM, ?<grazia at stat.columbia.edu> wrote:

Hi all,

I have a dataset of individuals where the variable ID corresponds to the
identification of the household where the individual lives. rel.head stands
for the relationship with the household head. so rel.head=1 is the household
head, rel.head=2 is the spouse, rel.head=3 is the children.

Here is an example to see how it looks like:

df<-data.frame(ID=c("17100", "17100", "17101", "17102", "17103", "17103",
? ? ? ? ? ? ? ? ? ? "17104", "17104", "17104", "17105", "17105"),
?rel.head=c("1","3","1","1","1", "2", "1", "2", "3", "1", "3"))


I want to add a dummy variable that is equal to 1 when these conditions
held simultaneously :

a) the number of rows with same ID is equal to 2
b) the variable rel.head=1 and rel.head=3


So my ideal output is:

? ID ? ? ?rel.head ? added.dummy
1 ?17100 ? ? ? ?1 ? ? ? ? ? 1
2 ?17100 ? ? ? ?3 ? ? ? ? ? 1
3 ?17101 ? ? ? ?1 ? ? ? ? ? 0
4 ?17102 ? ? ? ?1 ? ? ? ? ? 0
5 ?17103 ? ? ? ?1 ? ? ? ? ? 0
6 ?17103 ? ? ? ?2 ? ? ? ? ? 0
7 ?17104 ? ? ? ?1 ? ? ? ? ? 0
8 ?17104 ? ? ? ?2 ? ? ? ? ? 0
9 ?17104 ? ? ? ?3 ? ? ? ? ? 0
10 17105 ? ? ? ?1 ? ? ? ? ? 1
11 17105 ? ? ? ?3 ? ? ? ? ? 1

Is there a simple way to do that?
Can somebody help?

Thanks in advance,
Grazia