trafo: Modifications of Transformations

In mistr: Mixture and Composite Distributions

Modifications of Transformations

Description

The function modifies the given object and adds the transformation expressions.

Usage

trafo(O, type = "new", trans, invtrans, print, deriv, operation, value = 0)

Arguments

O	distribution object.
type	type of modification to be performed, default: 'new'.
trans	transformation expression.
invtrans	inverse transformation expression.
print	print expression.
deriv	derivative expression.
operation	string indicating which operation is performed.
value	numeric value used in operation, default: 0.

Details

trafo is the main function used in the transformation framework. The function offers four types of possible modifications. Note, that all expressions must use X to indicate the object in the transformation.

type = "init": Initializes the needed lists for transformations and adds the first expressions. This type should be used only with yet untransformed distributions as the first modification. All arguments must be set.

type = "new": Adds a new transformation to the current ones. This must be used only on already transformed distributions. All arguments must be set.

type = "update": Updates previous expression. This is useful when same transformation is used twice in a row. All arguments except operation must be set.

type = "go_back": Uses to history to reverse the previous transformation. Useful if inverse of previous transformation is evaluated. Only object and type must be specified.

Value

Transformed distribution object.

Examples

#init
P <- poisdist(5) ; x <- 5
P2 <- trafo(P, type = "init", trans = bquote(X + .(x)),
            invtrans = bquote(X - .(x)), print = bquote(X + .(x)),
            deriv = quote(1), operation = "+", value = x)
P2

#new
x = 3
P3 <- trafo(P2, type = "new", trans = bquote(.(x) * X),
            invtrans = bquote(X/.(x)), print = bquote(.(x) * X),
            deriv = bquote(1/.(x)), operation = "*", value = x)
P3

#update
x = 7 
P4 <- trafo(P3, type = "update", trans = bquote(.(x) * X),
            invtrans = bquote(X/.(x)), print = bquote(.(x) * X),
            deriv = bquote(1/.(x)), value = x)
P4

#go_back
P5 <- trafo(P4, type = "go_back")
P5

mistr documentation built on March 7, 2023, 7:42 p.m.