I would like to set column widths (for all the 3 columns) in this data set, as: anim=1-10; sireid=11-20; damid=21-30. Some columns have missing values.
anim=c("1A038","1C467","2F179","38138","030081")
sireid=c("NA","NA","1W960","1W960","64404")
damid=c("NA","NA","1P119","1P119","63666")
mydf=data.frame(anim,sireid,damid)
From reading your question as well as your comments to previous answers, it seems to me that you are trying to create a fixed width file with your data. If this is the case, you can use the function write.fwf in package gdata:
Load the package and create a temporary output file:
library(gdata)
ff <- tempfile()
Write your data in fixed width format to the temporary file:
write.fwf(mydf, file=ff, width=c(10,10,10), colnames=FALSE)
Read the file with scan and print the results (to demonstrate fixed width output):
zz <- scan(ff, what="character", sep="\n")
cat(zz, sep="\n")
1A038 NA NA
1C467 NA NA
2F179 1W960 1P119
38138 1W960 1P119
030081 64404 63666
Delete the temporary file:
unlink(ff)