GammaDist {base} | R Documentation |
Density, distribution function, quantile function and random
generation for the Gamma distribution with parameters shape
and
scale
.
dgamma(x, shape, scale=1, log = FALSE) pgamma(q, shape, scale=1, lower.tail = TRUE, log.p = FALSE) qgamma(p, shape, scale=1, lower.tail = TRUE, log.p = FALSE) rgamma(n, shape, scale=1)
x, q |
vector of quantiles. |
p |
vector of probabilities. |
n |
number of observations. |
shape, scale |
shape and scale parameters. |
log, log.p |
logical; if TRUE, probabilities p are given as log(p). |
lower.tail |
logical; if TRUE (default), probabilities are P[X <= x], otherwise, P[X > x]. |
If scale
is omitted, it assumes the default value of 1
.
The Gamma distribution with parameters shape
= a
and scale
= b has density
f(x) = 1/(b^a Gamma(a)) x^(a-1) e^-(x/b)
for x > 0, a > 0 and b > 0.
dgamma
gives the density,
pgamma
gives the distribution function
qgamma
gives the quantile function, and
rgamma
generates random deviates.
gamma
for the Gamma function, dbeta
for
the Beta distribution and dchisq
for the chi-square
distribution which is a special case of the Gamma distribution.
-log(dgamma(1:4, shape=1)) p <- (1:9)/10 pgamma(qgamma(p,shape=2), shape=2) 1 - 1/exp(qgamma(p, shape=1))