another approach is:
df <- data.frame(j1999 = c(0,0,0,0,1,0), j2000 = c(NA,1,1,1,0,0),
j2001 = c(1,0,1,0,0,0))
years <- as.numeric(gsub("^[^0-9]+", "", names(df)))
ind <- apply(sapply(df, "==", 1), 1, function (x) which(x)[1])
df$year <- years[ind]
I hope it helps.
Best,
Dimitris
On 5/4/2011 1:52 PM, Albert-Jan Roskam wrote:
Hello,
A simple question perhaps, but how do I, within each row, find the first
occurence of the number 1 in the df below? I want to use this position to
programmatically create the variable 'year'. I'v come up with a solution, but I
find it downright ugly. Is there a simpler way? I was hoping for a useful
built-in function that I don;t yet know about.
df<- data.frame(j1999=c(0,0,0,0,1,0), j2000=c(NA, 1, 1, 1, 0, 0), j2001=c(1, 0,
1, 0, 0, 0), year=c(2001, 2000, 2000, 2000, 1999, NA))
library(gsubfn)
x<- apply(df==1, 1, which)
giveYear<- function(df) { return( as.numeric(gsubfn("^[^0-9]+", "",
names(df)[1])) ) }
df$year2<- sapply(x, giveYear)
Thanks in advance!
Cheers!!
Albert-Jan
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Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center
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