Setting column width in a data set - r

Question

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)

Answer 1

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)

Answer 2

You can also write fixed width output for numbers and strings using the sprintf() function, which derives from C's counterpart.
For instance, to pad integers with 0s:
sprintf("%012d",99)
To pad with spaces:
sprintf("%12d",123)
And to pad strings:
sprintf("%20s","hello world")
The options for formatting are found via ?sprintf and there are many guides to formatting C output for fixed width.

Answer 3

It sounds like you're coming from a SAS background, where character variables should have explicit lengths specified to avoid unexpected truncations. In R, you don't need to worry about this. A character string has exactly as many characters as it needs, and automatically expands and contracts as its contents change.
One thing you should be aware of, though, is silent conversion of character variables to factors in a data frame. However, unless you change the contents at a later point in time, you should be able to live with the default.