PearsonIII | R Documentation |
Density, distribution function, quantile function and random generation for the Pearson type III (aka Gamma) distribution.
dpearsonIII(x, shape, location, scale, params, log = FALSE)
ppearsonIII(q, shape, location, scale, params, lower.tail = TRUE,
log.p = FALSE)
qpearsonIII(p, shape, location, scale, params, lower.tail = TRUE,
log.p = FALSE)
rpearsonIII(n, shape, location, scale, params)
x , q |
vector of quantiles. |
p |
vector of probabilities. |
n |
number of observations. |
shape |
shape parameter of Pearson type III distribution. |
location |
location parameter of Pearson type III distribution. |
scale |
scale parameter of Pearson type III distribution. |
params |
vector/list of length 3 containing parameters |
log , log.p |
logical; if |
lower.tail |
logical; if |
Essentially, the above functions are wrappers for dgamma
,
pgamma
, qgamma
and rgamma
contained in package
stats
.
As a minor (but important) extension, negative scale
parameters
(which reflect the distribution at location
) are
permitted to allow for negative skewness.
The probability density function with parameters shape
=a
,
scale
=s
and location
=\lambda
is thus given by
f(x)= \frac{1}{|s|^a \Gamma(a)} |x-\lambda|^{a-1}
e^{-\frac{x-\lambda}{s}}
for s\ne 0
, a>0
and
\frac{x-\lambda}{s}\ge 0
.
dpearsonIII
gives the density, ppearsonIII
gives the
distribution function, qpearsonIII
gives the quantile function,
and rpearsonIII
generates random deviates.
Martin Becker martin.becker@mx.uni-saarland.de
See the references in GammaDist
.
GammaDist
,
PearsonDS-package
,
Pearson
## define Pearson type III parameter set with shape=3, location=1, scale=-2
pIIIpars <- list(shape=3, location=1, scale=-0.5)
## calculate probability density function
dpearsonIII(-4:1,params=pIIIpars)
## calculate cumulative distribution function
ppearsonIII(-4:1,params=pIIIpars)
## calculate quantile function
qpearsonIII(seq(0.1,0.9,by=0.2),params=pIIIpars)
## generate random numbers
rpearsonIII(5,params=pIIIpars)
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