urf | R Documentation |
UNU.RAN random variate generator for the F distribution with
with df1
and df2
degrees of freedom.
It also allows sampling from the truncated distribution.
[Special Generator] – Sampling Function: F.
urf(n, df1, df2, lb=0, ub=Inf)
n |
size of required sample. |
df1, df2 |
(strictly positive) degrees of freedom. Non-integer values allowed. |
lb |
lower bound of (truncated) distribution. |
ub |
upper bound of (truncated) distribution. |
The F distribution with df1 =
n1 and df2 =
n2 degrees of freedom has density
f(x) = Gamma((n1 + n2)/2) / (Gamma(n1/2) Gamma(n2/2)) * (n1/n2)^(n1/2) x^(n1/2 - 1) * (1 + (n1/n2) x)^-(n1 + n2)/2
for x > 0.
The generation algorithm uses fast numerical inversion. The parameters
lb
and ub
can be used to generate variates from
the F distribution truncated to the interval (lb
,ub
).
This function is wrapper for the UNU.RAN class in R.
Compared to rf
, urf
is faster, especially for
larger sample sizes.
However, in opposition to rf
vector arguments are ignored,
i.e. only the first entry is used.
Josef Leydold and Wolfgang H\"ormann unuran@statmath.wu.ac.at.
W. H\"ormann, J. Leydold, and G. Derflinger (2004): Automatic Nonuniform Random Variate Generation. Springer-Verlag, Berlin Heidelberg
runif
and .Random.seed
about random number
generation, unuran
for the UNU.RAN class, and
rf
for the R built-in generator.
## Create a sample of size 1000 x <- urf(n=1000,df1=3,df2=5)
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