Zapois {VGAM} | R Documentation |
Zero-Altered Poisson Distribution
Description
Density, distribution function, quantile function and random
generation for the zero-altered Poisson distribution with
parameter pobs0
.
Usage
dzapois(x, lambda, pobs0 = 0, log = FALSE)
pzapois(q, lambda, pobs0 = 0)
qzapois(p, lambda, pobs0 = 0)
rzapois(n, lambda, pobs0 = 0)
Arguments
x , q |
vector of quantiles. |
p |
vector of probabilities. |
n |
number of observations.
If |
lambda |
Vector of positive means. |
pobs0 |
Probability of zero, called |
log |
Logical. Return the logarithm of the answer? |
Details
The probability function of Y
is 0 with probability
pobs0
, else a positive
Poisson(\lambda)
.
Value
dzapois
gives the density,
pzapois
gives the distribution function,
qzapois
gives the quantile function, and
rzapois
generates random deviates.
Note
The argument pobs0
is recycled to the required length,
and must have values which lie in the interval [0,1]
.
Author(s)
T. W. Yee
See Also
zapoisson
,
Gaitdpois
,
dzipois
.
Examples
lambda <- 3; pobs0 <- 0.2; x <- (-1):7
(ii <- dzapois(x, lambda, pobs0))
max(abs(cumsum(ii) - pzapois(x, lambda, pobs0))) # Should be 0
table(rzapois(100, lambda, pobs0))
table(qzapois(runif(100), lambda, pobs0))
round(dzapois(0:10, lambda, pobs0) * 100) # Should be similar
## Not run: x <- 0:10
barplot(rbind(dzapois(x, lambda, pobs0), dpois(x, lambda)),
beside = TRUE, col = c("blue", "green"), las = 1,
main = paste0("ZAP(", lambda, ", pobs0 = ", pobs0, ") [blue]",
"vs Poisson(", lambda, ") [green] densities"),
names.arg = as.character(x), ylab = "Probability")
## End(Not run)