one way is the following:
m <- data.frame(x = rnorm(100), y = rnorm(100), z = rnorm(100))
m$z[sample(100, 20)] <- NA
m$z.new <- ifelse(is.na(m$z), m$x, m$z)
I hope it helps.
Best,
Dimitris
On 9/8/2010 8:17 PM, Jakob Hedegaard wrote:
Hi list,
I have a data frame (m) with 169221 rows and 10 columns and would like to make
a new column containing the content of column 3 but replace the NAs in column 3
with the data in column 1 (from the same row as the NA in column 3). Column 1
has data in all rows.
My first attempt was:
for (i in 1:169221){
if (is.na(m[i,3])==TRUE){
m[i,11]<- as.character(m[i,1])}
else{
m[i,11]<- as.character(m[i,3])}
}
Works - but takes too long time.
I would appreciate alternative solutions.
Best regards, Jakob
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--
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center
Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
Fax: +31/(0)10/7043014
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
