Hi all,

I have been trying to use zeroinfl() with the pscl package with R version 2.1.1. and with the newest versions of the contrib packages compatible with R 2.1.1.

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")
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)
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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