mistr (version 0.0.6)

trafo: 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)

Value

Transformed distribution object.

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.

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