zero truncated poisson regression
On Sun, 31 Jul 2011, Iasonas Lamprianou wrote:
Thanks Pscl seems to be a sensible option. I have the counts variable with the name "N". This variable can only take values bigger than zero! I have two explanatory variables with the names "type" and "diam" but when I run hpm <- hurdle(n ~ type+diam, data = an, dist = "poisson") I get the message "invalid dependent variable, minimum count is not zero". Well, I know that N>0, that is why want to run a zero-truncated model. But I must be missing something...and the manual does not seem to help a lot... Can anyone help please?
As previously pointed out by others on this list: hurdle() is not what you
are looking for (although it is related to what you want to do). The
hurdle() model is a two-part model consisting of a zero-truncated count
part and a binary part for modeling N=0 vs N>0. See also
vignette("countreg", package = "pscl") for details.
As you don't need the binary hurdle part, you cannot use hurdle()
directly.
This is why the package "countreg" on R-Forge provides the function
zerotrunc() which essentially does the same thing as the count part in
hurdle().
install.packages("countreg", repos = "http://R-Forge.R-project.org")
library("countreg")
m <- zerotrunc(n ~ type + diam, data = an, dist = "poisson")
summary(m)
? Dr. Iasonas Lamprianou Department of Social and Political Sciences University of Cyprus
________________________________ From: Mitchell Maltenfort <mmalten at gmail.com> To: Iasonas Lamprianou <lamprianou at yahoo.com>; "r-help at r-project.org" <r-help at r-project.org> Sent: Sunday, 31 July 2011, 20:45 Subject: Re: [R] zero truncated poisson regression Pscl package. On 7/31/11, Iasonas Lamprianou <lamprianou at yahoo.com> wrote: Dear friends, does anyone know how I can run a zero truncated poisson regression using R (or even SPSS)? Dr. Iasonas Lamprianou Department of Social and Political Sciences University of Cyprus ??? [[alternative HTML version deleted]] -- Sent from my mobile device Due to the recession, requests for instant gratification will be deferred until arrears in scheduled gratification have been satisfied.
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