hyperdirichlet (version 1.5-1)

hyperdirichlet: The Hyperdirichlet distribution

Description

Create, coerce to, or test for an object of class hyperdirichlet

Usage

hyperdirichlet(x, NC, pnames = character(), validated=FALSE)
is.hyperdirichlet(x)
as.hyperdirichlet(x, calculate_NC = FALSE , ...)

Arguments

x

Object to be coerced or tested for

NC

Normalizing constant

pnames

names of the columns with length-0 default resulting in the print method using column names p1, p2, etc

validated

Boolean. Setting to TRUE is taken to mean that x is known to be ‘proper’ (i.e. x is normalizable), but the normalizing constant is not necessarily known. Default FALSE is taken to mean that x is not known to be proper: it is possible that x is not normalizable so cannot correspond to a PDF.

Setting to FALSE means that the object will be passed to is.proper() for checking; this can be time-consuming. The flag is set to TRUE ab initio for dirichlet() and gd() because these distributions have an analytical expression for the normalizing constant

calculate_NC

Boolean, with default FALSE meaning not to calculate the normalizing constant and TRUE meaning to calculate it

...

Further arguments passed to adaptIntegrate()

Value

Functions hyperdirichlet() and as.hyperdirichlet() return a hyperdirichlet object; function is.hyperdirichlet() returns a Boolean.

Details

To determine the normalization constant, use something like a <- as.hyperdirichlet(a,calculate_NC= TRUE).

Matrices may be coerced to a hyperdichlet object using as.hyperdirichlet(): the call is dispatched to matrix_to_HD() (qv).

If x is a matrix, be sure to specify the bernoulli argument, which is passed on to matrix_to_HD()

See Also

B,extract,matrix_to_HD

Examples

(a <- uniform(3))
a[c(TRUE,TRUE,FALSE)] <- 0.3
## Not run: ------------------------------------
# (a <- as.hyperdirichlet(a, calculate_NC = TRUE))  # recommended way to calculate NC
## ---------------------------------------------

(b <- dirichlet(1:3))
as.hyperdirichlet(b)          # "forgets" the normalizing constant

## Not run: ------------------------------------
# as.hyperdirichlet(b, TRUE)    # recalculates NC; accuracy tolerable
#                               # (analytic answer = 1/60)
## ---------------------------------------------

## Not run: ------------------------------------
#   # takes a long time
# op <- options()
# options(warn = -1)
# x <- dirichlet(rep(2,4)) + justpairs(matrix(1,4,4))
# f <- function(p){p[1]>p[2]}
# probability(x,f) # should be 0.5: distribution is symmetric
## ---------------------------------------------


# following example reveals a bug in versions <= 1.3:
d <- dirichlet(1:3)
colMeans(rhyperdirichlet(1e3,d))
# result should be (1:3)/6
# implementation >= 1.4 includes a bugfix sent by Simon Byrne