Anders Schwartz Corr wrote: > Dear R-help, > > I am trying to impute missing data for the first time using R. The norm > package seems to work for me, but the missing values that it returns seem > odd at times -- for example it returns negative values for a variable that > should only be positive. Does this matter in data analysis, and/or is > there a way to limit the imputed values to be within the minimum and > maximum of the actual data? Below is the code I am using. > > Thanks, > > Anders Corr > Ph.D. Candidate
Yes that matters. That's one reason I wrote the aregImpute function in the Hmisc package. By default it uses predictive mean matching so it can't produce illegal values. Frank > > > #DOWNLOAD DATA (61Kb) > download.file("http://www.people.fas.harvard.edu/~corr/tc.csv","C:/R") > > #RUN NORM > tc <- read.csv("tc.csv", header = TRUE) > rngseed(1234567) #set random number generator seed > s <- prelim.norm(tc) > thetahat <- em.norm(s) #find the MLE for a starting value > theta <- da.norm(s,thetahat,steps=20,showits=TRUE,return.ymis=TRUE) #take 20 > steps > ximp <- imp.norm(s,thetahat,tc) #impute missing data under the MLE > -- Frank E Harrell Jr Professor and Chair School of Medicine Department of Biostatistics Vanderbilt University ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html