One-inflated Zeta Distribution Family Function
Fits a 1-inflated zeta distribution.
oizeta(lpstr1 = "logitlink", lshape = "loglink",
type.fitted = c("mean", "shape", "pobs1", "pstr1", "onempstr1"),
ishape = NULL, gpstr1 = ppoints(8), gshape = exp((-3:3) / 4), zero = NULL)lpstr1, lshape |
For |
gpstr1, gshape, ishape |
For initial values.
See |
type.fitted, zero |
See |
The 1-inflated zeta distribution is a mixture
distribution of the
zeta
distribution with some probability of obtaining a (structural) 1.
Thus there are two sources for obtaining the value 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. Lots of data is needed to estimate the parameters accurately. Usually, probably the shape parameter is best modelled as intercept-only.
Thomas W. Yee
## Not run: odata <- data.frame(x2 = runif(nn <- 1000)) # Artificial data odata <- transform(odata, pstr1 = logitlink(-1 + x2, inverse = TRUE), shape = exp(-0.5)) odata <- transform(odata, y1 = roizeta(nn, shape, pstr1 = pstr1)) with(odata, table(y1)) fit1 <- vglm(y1 ~ x2, oizeta(zero = "shape"), data = odata, trace = TRUE) coef(fit1, matrix = TRUE) ## End(Not run)
Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.