On Thu, 22 Jan 2009, Simon Pickett wrote:
Hi all,
I have been trying to use zeroinfl() with the pscl package with R
version 2.1.1.
That version is ancient, please upgrade.
and with the newest versions of the contrib packages
compatible with R 2.1.1.
A version number for pscl would have been most helpful. I'm pretty sure
that this is a version of "pscl" prior to the re-design of the count
regression functionality, i.e., a version of the package which does not
have the vignette you refer to. Surprisingly, the vignette applies to
the version of the package which actually contains the vignette.
In any case, please use the most recent version of pscl.
I have read the examples, the vignette and all the posts relating to
zeroinfl() but I am still confused as to how to structure the model.
Here is a small example; the error message is the same for big data sets
library(mvtnorm,lib.loc="C:/Documents and Settings/simonp/My Documents/R backup
library")
Not needed here.
library(pscl,lib.loc="C:/Documents and Settings/simonp/My Documents/R backup
library")
y<-c(0,0.2,0.4,0.7,0,0,0,0.8,0,0,0,0,0)
Non-integer counts are not allowed. (If these stem from division by some
offset, please do not divide and use the offset instead.)
hth,
Z
x<-c(3,4,5,2,3,6,3,7,4,8,5,8,3)
m1<-zeroinfl(y~x|x)
Zero-Inflated Count Model
Using logit to model zero vs non-zero
Using Poisson for counts
Error in terms.formula(formula, data = data) :
argument is not a valid model
Can anyone shed any light please?
Simon.
Dr. Simon Pickett
Research Ecologist
Land Use Department
Terrestrial Unit
British Trust for Ornithology
The Nunnery
Thetford
Norfolk
IP242PU
01842750050
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