onacopula | R Documentation |
Constructing (outer) nested Archimedean copulas (class
outer_nacopula
) is most conveniently done via
onacopula()
, using a nested C(...)
notation.
Slightly less conveniently, but with the option to pass a list
structure, onacopulaL()
can be used, typically from inside
another function programmatically.
onacopula (family, nacStructure)
onacopulaL(family, nacList)
nac2list(x)
family |
either a |
nacStructure |
a “formula” of the form
Note that |
nacList |
a
|
x |
an |
onacopula[L]()
:
An outer nested Archimedean copula object, that is, of class
"outer_nacopula"
.
nac2list
: a list
exactly like the naclist
argument to onacopulaL
.
Those of the Archimedean families, for example, copGumbel
.
The class definitions "nacopula"
,
"outer_nacopula"
, and "acopula"
.
## Construct a ten-dimensional Joe copula with parameter such that
## Kendall's tau equals 0.5
theta <- copJoe@iTau(0.5)
C10 <- onacopula("J",C(theta,1:10))
## Equivalent construction with onacopulaL():
C10. <- onacopulaL("J",list(theta,1:10))
stopifnot(identical(C10, C10.),
identical(nac2list(C10), list(theta, 1:10)))
## Construct a three-dimensional nested Gumbel copula with parameters
## such that Kendall's tau of the respective bivariate margins are 0.2
## and 0.5.
theta0 <- copGumbel@iTau(.2)
theta1 <- copGumbel@iTau(.5)
C3 <- onacopula("G", C(theta0, 1, C(theta1, c(2,3))))
## Equivalent construction with onacopulaL():
str(NAlis <- list(theta0, 1, list(list(theta1, c(2,3)))))
C3. <- onacopulaL("Gumbel", NAlis)
stopifnot(identical(C3, C3.))
## An exercise: assume you got the copula specs as character string:
na3spec <- "C(theta0, 1, C(theta1, c(2,3)))"
na3call <- str2lang(na3spec) # == parse(text = na3spec)[[1]]
C3.s <- onacopula("Gumbel", na3call)
stopifnot(identical(C3, C3.s))
## Good error message if the component ("coordinate") indices are wrong
## or do not match:
err <- try(onacopula("G", C(theta0, 2, C(theta1, c(3,2)))))
## Compute the probability of falling in [0,.01]^3 for this copula
pCopula(rep(.01,3), C3)
## Compute the probability of falling in the cube [.99,1]^3
prob(C3, rep(.99, 3), rep(1, 3))
## Construct a 6-dimensional, partially nested Gumbel copula of the form
## C_0(C_1(u_1, u_2), C_2(u_3, u_4), C_3(u_5, u_6))
theta <- 2:5
copG <- onacopulaL("Gumbel", list(theta[1], NULL, list(list(theta[2], c(1,2)),
list(theta[3], c(3,4)),
list(theta[4], c(5,6)))))
set.seed(1)
U <- rCopula(5000, copG)
pairs(U, pch=".", gap=0, labels = as.expression( lapply(1:dim(copG),
function(j) bquote(italic(U[.(j)]))) ))
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