Zero-Inflated Geometric Distribution
Density, and random generation
for the zero-inflated geometric distribution with parameter pstr0.
dzigeom(x, prob, pstr0 = 0, log = FALSE) pzigeom(q, prob, pstr0 = 0) qzigeom(p, prob, pstr0 = 0) rzigeom(n, prob, pstr0 = 0)
x, q |
vector of quantiles. |
p |
vector of probabilities. |
prob |
see |
n |
Same as in |
pstr0 |
Probability of structural zero (ignoring the geometric distribution), called phi. The default value corresponds to the response having an ordinary geometric distribution. |
log |
Logical. Return the logarithm of the answer? |
The probability function of Y is 0 with probability phi, and geometric(prob) with probability 1-phi. Thus
P(Y=0) = phi + (1-phi) * P(W=0)
where W is distributed geometric(prob).
dzigeom gives the density,
pzigeom gives the distribution function,
qzigeom gives the quantile function, and
rzigeom generates random deviates.
The argument pstr0 is recycled to the required length, and
must have values which lie in the interval [0,1].
These functions actually allow for zero-deflation.
That is, the resulting probability of a zero count
is less than the nominal value of the parent
distribution.
See Zipois for more information.
T. W. Yee
prob <- 0.5; pstr0 <- 0.2; x <- (-1):20
(ii <- dzigeom(x, prob, pstr0))
max(abs(cumsum(ii) - pzigeom(x, prob, pstr0))) # Should be 0
table(rzigeom(1000, prob, pstr0))
## Not run: x <- 0:10
barplot(rbind(dzigeom(x, prob, pstr0), dgeom(x, prob)),
beside = TRUE, col = c("blue","orange"),
ylab = "P[Y = y]", xlab = "y", las = 1,
main = paste("zigeometric(", prob, ", pstr0 = ", pstr0,
") (blue) vs",
" geometric(", prob, ") (orange)", sep = ""),
names.arg = as.character(x))
## End(Not run)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.