One-inflated Positive Poisson Distribution Family Function
Fits a 1-inflated positive Poisson distribution.
oipospoisson(lpstr1 = "logitlink", llambda = "loglink",
type.fitted = c("mean", "lambda", "pobs1", "pstr1", "onempstr1"),
ilambda = NULL, gpstr1 = (1:19)/20, gprobs.y = (1:19)/20,
imethod = 1, zero = NULL)lpstr1, llambda |
For |
ilambda, gpstr1, gprobs.y, imethod |
For initial values.
See |
type.fitted, zero |
See |
The 1-inflated positive Poisson distribution is a mixture
distribution of the
positive (0-truncated) Poisson
distribution with some probability of obtaining a (structural) 1.
Thus there are two sources for obtaining the value 1.
It is similar to a zero-inflated Poisson model, except
the Poisson is replaced by a positive Poisson and the 0 is replaced
by 1.
This distribution is written here
in a way that retains a similar notation to the
zero-inflated Poisson, i.e., the
probability P[Y=1] involves another parameter phi.
See zipoisson.
This family function can handle multiple responses.
An object of class "vglmff" (see vglmff-class).
The object is used by modelling functions such as vglm,
rrvglm and vgam.
Under- or over-flow may occur if the data is ill-conditioned.
Thomas W. Yee
## Not run: set.seed(1) pdata <- data.frame(x2 = runif(nn <- 1000)) # Artificial data pdata <- transform(pdata, pstr1 = 0.5, lambda = exp(3 - x2)) pdata <- transform(pdata, y1 = roipospois(nn, lambda, pstr1 = pstr1)) with(pdata, table(y1)) fit1 <- vglm(y1 ~ x2, oipospoisson, data = pdata, trace = TRUE) coef(fit1, matrix = TRUE) ## End(Not run)
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