Thank yot for your excellent detailed explanation! Sigalit.
On 10/24/07, Ted Harding <[EMAIL PROTECTED]> wrote: > > On 24-Oct-07 08:51:30, sigalit mangut-leiba wrote: > > hello, > > I want to do a single Imputation method on binary data set. > > Is it possible to use imp.cat from CAT package? > > I have a problem defining "theta" when data is binary. > > Do you know any references on the subject? > > Thank you, > > Sigalit. > > There should be no problem in principle. However, you must > make sure to do things in the correct sequence. > > 1. Make sure your data are in a matrix, not a dataframe, > where the rows correzspond to cases and the columns > correspond to variables. (In passing: you must of > course have at least two variables). If your data are > in a dataframe Y in the first instance, first do > > X <- as.matrix(Y) > > 2. Make sure that the binary outcomes are coded as 1 and 2, > not 0 and 1. Missing values should be coded as NA. If > the outcomes are 0 and 1, then do > > X <- X+1 > > 3. Now do the preliminary step, which creates a specially > formatted representation of the data, missing value > patterns, etc. (and of course first load the 'cat' package): > > library(cat) > s <- prelim.cat(X) > > where X is your data matrix as in (1) and (2). > > 4. Next, the maximum-likelihood estimation: > > t <- em.cat(s) > > 5. Now you can embark on as many imputations as you wish, > alternating between da.cat() and imp.cat(): > > t <- da.cat(s,t) > imp.1 <- imp.cat(s,t) > > t <- da.cat(s,t) > imp.2 <- imp.cat(s,t) > > ... > > More details can be found in the documentation for the > functions listed by > > library(help=cat) > > e.g. ?prelim.cat, ?em.cat, ?da.cat, ?imp.cat, etc. > > The above is for a straightforward imputation of missing > values in a dataset of caregorical variables, and does not > incorporate any special modelling considerations. See also: > ?ecm.cat and other functions. > > Hoping this helps, > Ted. > > -------------------------------------------------------------------- > E-Mail: (Ted Harding) <[EMAIL PROTECTED]> > Fax-to-email: +44 (0)870 094 0861 > Date: 24-Oct-07 Time: 10:59:01 > ------------------------------ XFMail ------------------------------ > [[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.