ztpoisson {countreg} | R Documentation |
Family object for specification of zero-truncated Poisson models
as a glm
.
ztpoisson()
The ztpoisson
family allows to estimate zero-truncated
Poisson regression models as generalized linear models. As in
the zerotrunc
function, the link function is a
log-link between the mean λ of the untruncated Poisson
distribution and the linear predictor. This corresponds to a
non-canonical link between for the mean of the zero-truncated
Poisson distribution which does not have a closed-form representation.
An object of class "family"
.
## data data("CrabSatellites", package = "countreg") cs <- subset(CrabSatellites, subset = satellites > 0) cs$color <- as.numeric(cs$color) ## model ztp1 <- glm(satellites ~ width + color, data = cs, family = ztpoisson) ztp2 <- zerotrunc(satellites ~ width + color, data = cs) summary(ztp1) summary(ztp2)