Check out: https://stat.ethz.ch/pipermail/r-help/2010-February/228228.html
On Sun, Feb 28, 2010 at 2:39 AM, Christian Raschke <cras...@tigers.lsu.edu> wrote: > Dear R-List, > > My questions concerns missing values. Specifically, is is possible to > use different "types" of missingness in a dataset and not a > one-size-fits-all NA? > For example, data may be missing because of an outright refusal by a > respondent to answer a question, or because she didn't know an answer, > or because the item simply did not apply. In later analysis it is > sometimes useful to be able to distinguish between the cases, but > nonetheless have them all treated as missing when using, say, lm( ). > In Stata this is possible by using different missing value indicators. > The standard one is a period '.' whereas '.a' and '.b' etc are treated > as missing too, but can all be distinguished from another (they are even > ordinal such that . < .a < .b). > To give a simplistic example in R, let > > > dat <- data.frame( > + hours = c(36, 40, 40, 0, 37.5, 0, 36, 20, 40), > + wage = c( 15.5, 7.5, 8, -1, 17.5, -1, -2, 13, -2)) > > dat > hours wage > 1 36.0 15.5 > 2 40.0 7.5 > 3 40.0 8.0 > 4 0.0 -1.0 > 5 37.5 17.5 > 6 0.0 -1.0 > 7 36.0 -2.0 > 8 20.0 13.0 > 9 40.0 -2.0 > > > where for wages -1 indicates "didn't work" and -2 indicates "refused to > respond". How could I replace the negative values for wages with > missingness indicators to use the data frame in for instance lm( ), but > later operate only on those observations who "refused to respond"? > Of course I can always work around this somehow, especially in this easy > example, but as data frames get larger and cases more complex the > workarounds seem more and more klutzy to me. > So, if there is an easy way to do this that I have overlooked, I would > be grateful for any advice or references. > > Best, > Christian > > -- > Christian Raschke > Department of Economics > and > ISDS Research Lab (HSRG) > Louisiana State University > Patrick Taylor Hall, Rm 2128 > Baton Rouge, LA 70803 > cras...@lsu.edu > > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
