Zero-Altered Poisson Distribution
Density, distribution function, quantile function and random generation
for the zero-altered Poisson distribution with parameter pobs0.
dzapois(x, lambda, pobs0 = 0, log = FALSE) pzapois(q, lambda, pobs0 = 0) qzapois(p, lambda, pobs0 = 0) rzapois(n, lambda, pobs0 = 0)
x, q |
vector of quantiles. |
p |
vector of probabilities. |
n |
number of observations.
If |
lambda |
Vector of positive means. |
pobs0 |
Probability of zero, called pobs0.
The default value of |
log |
Logical. Return the logarithm of the answer? |
The probability function of Y is 0 with probability
pobs0, 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 pobs0 is recycled to the required length, and
must have values which lie in the interval [0,1].
T. W. Yee
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 = paste("ZAP(", lambda, ", pobs0 = ", pobs0, ") [blue] vs",
" Poisson(", lambda, ") [green] densities", sep = ""),
names.arg = as.character(x), ylab = "Probability")
## End(Not run)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.