On Mon, 1 Aug 2011, Iasonas Lamprianou wrote:
Thank you, it works! And the estimates (as well as the standard errors)
seem to be more reasonable now, compared to the "normal" Poisson model.
Thank you. However, I tried to find a manual? (although I did manage to
find the paper published in the Journal of Statistical Software. For
example, how does ?zerotrunc return?
The package still needs some proper documentation and some cleaning up
which is why it is not yet on CRAN.
The code, however, is well tested because it is exactly the code
underlying the hurdle() function in "pscl". Hence, the "zerotrunc" objects
are rather similar in many respect to "hurdle" objects. Starting from the
JSS paper you should hopefully be able to find your way.
Z
?
Dr. Iasonas Lamprianou
Department of Social and Political Sciences
University of Cyprus
________________________________
From: Achim Zeileis <achim.zeil...@uibk.ac.at>
To: Iasonas Lamprianou <lampria...@yahoo.com>
Cc: Mitchell Maltenfort <mmal...@gmail.com>; "r-help@r-project.org"
<r-help@r-project.org>
Sent: Monday, 1 August 2011, 10:10
Subject: Re: [R] 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 <mmal...@gmail.com>
To: Iasonas Lamprianou <lampria...@yahoo.com>; "r-help@r-project.org"
<r-help@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 <lampria...@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
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