| Zapois {VGAM} | R Documentation |
Density, distribution function, quantile function and random generation
for the zero-altered Poisson distribution with parameter p0.
dzapois(x, lambda, p0 = 0, log = FALSE) pzapois(q, lambda, p0 = 0) qzapois(p, lambda, p0 = 0) rzapois(n, lambda, p0 = 0)
x, q |
vector of quantiles. |
p |
vector of probabilities. |
n |
number of observations. Must be a single positive integer. |
lambda |
Vector of positive means. |
p0 |
Probability of zero, called p0.
The default value of p0=0 corresponds
to the response having a positive Poisson distribution.
|
log |
Logical. Return the logarithm of the answer? |
The probability function of Y is 0 with probability
p0, else a positive Poisson(lambda).
dzapois gives the density,
pzapois gives the distribution function,
qzapois gives the quantile function, and
rzapois generates random deviates.
The argument p0 is recycled to the required length, and
must have values which lie in the interval [0,1].
Thomas W. Yee
lambda = 3
p0 = 0.2
x = (-1):7
(i = dzapois(x, lambda, p0))
max(abs(cumsum(i) - pzapois(x, lambda, p0))) # Should be 0
table(rzapois(100, lambda, p0))
table(qzapois(runif(100), lambda, p0))
round(dzapois(0:10, lambda, p0) * 100) # Should be similar
## Not run:
x = 0:10
barplot(rbind(dzapois(x, lambda, p0), dpois(x, lambda)),
beside = TRUE, col = c("blue","green"),
main=paste("ZAP(", lambda, ", p0=", p0, ") (blue) vs",
" Poisson(", lambda, ") (green)", sep=""),
names.arg = as.character(x))
## End(Not run)