[gov2001-l] mix package

As a heads up, this was the product of a lot of collective frustration, error messages, and core dumps on the part of myself, Jens, Ben, Federico, and others. On other data sets, here are some things to watch out for (some of which are in the notes in the code) on other datasets: 1) Try to use as few categorical variables as possible; reserve them for things that really have no logical ordering. If you get an empty cells error message, this might be the problem. 2) If you declare a variable to be categorical, it really can't have zeros in it. This causes R to crash on my computer, and I think it is the reason for the core dumps on the server. 3) If a continuous variable is strongly skewed, try transforming it so that it is more approximately normal. This can be a reason for the em.mix stage to go haywire. 4) As always, watch out for linear dependencies in the data. I accidentally put log(x) and log(x^2) in at the same time and it wasn't happy. Likewise, if you have a dummy variable (say a country) for which all of the values of a different variable are missing (say GDP), then you can't include the dummy; there is nothing to pin down the values. 5) Make sure the data object is a matrix before you start the mix functions. Leaving it as a data frame produces a list cannot be coerced to double error message. 6) Most of the problems seem to arise when the data doesn't look exactly like you think it should look; look at it before running the mix functions. Cheers, Mike On Thu, 16 Dec 2004, Olivia Lau wrote: