[R-sig-ME] Mixed effect model, Hurdle function

Pin chanratana chanratana.pin at gmail.com
Fri Nov 18 05:29:10 CET 2016

Hi everyone here,

My name's Ratana, and I'm a Msc. student studying conservation ecology.

I'm new to the using of mixed effects model. I try to fit the mixed effect
models include an offset term (which is trapnight)  of my camera-trap data
by using hurdle function. The following are the model that I fit.

m1 <- hurdle(GI ~
depth+Ele+dRoad+offset(log(TN))|depth+Ele+offset(log(TN)), data=ndata2,
dist="poisson", zero.dist="poisson")

m2 <- hurdle(GI ~ depth+Ele+dRoad+offset(TN2)|depth+Ele+offset(TN2),
data=ndata2, dist="poisson", zero.dist="poisson")

GI: Giant ibis
depth: depth of waterholes
Ele: Elevation
dRoad: distance to Road
TN: Trap-night
TN2: standardize or scale of Trap-night

But, I could not fit model m1 and there are error message: Error in
glm.fit(X, Y, family = poisson(), weights = weights, offset = offsetx) :
NA/NaN/Inf in 'y'

Model m2 is work fine and the result look reasonable.

I would like to ask if anyone know, is the way I do with model 2 is correct
by standardize the Trap-night that's use for offset in the fitting model?
If it's ok to do so, is there any reference (that I can cite) regarding to
this kind of process ?



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