TITLE(Poisson @@ The Poisson Distribution)
USAGE(
dpois(x, lambda)
ppois(q, lambda)
qpois(p, lambda)
rpois(n, lambda)
)
ALIAS(dpois)
ALIAS(ppois)
ALIAS(qpois)
ALIAS(rpois)
ARGUMENTS(
ARG(x @@ vector of (positive) quantiles.)
ARG(p @@ vector of probabilities.)
ARG(n @@ number of random values to return.)
ARG(lambda @@ vector of positive means.)
)
DESCRIPTION(
These functions provide information about the Poisson distribution
with parameter LANG(lambda).  LANG(dpois) gives the density,
LANG(ppois) gives the distribution function LANG(qpois) gives the
quantile function and LANG(rpois) generates random deviates.
PARA
The Poisson distribution has density
DEQN(p(x) = OVER(SUP(greeklambda@@x) SUP(e@@-greeklambda) @@ x!)
  @@ p(x) = lambda^x exp(-lambda)/x!)
for EQN(x = 0, 1, 2, LDOTS).
)
EXAMPLES(
-log(dpois(0:7, lambda=1) * gamma(1+ 0:7))
Ni <- rpois(50, lam= 4); table(factor(Ni, 0:max(Ni)))
)
