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 ------------------------------ ______________________________________________ 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.