Reaction: A reaction (chance) edge in a decision tree

In rdecision: Decision Analytic Modelling in Health Economics

A reaction (chance) edge in a decision tree

Description

An R6 class representing a reaction (chance) edge in a decision tree.

Details

A specialism of class Arrow which is used in a decision tree to represent edges whose source nodes are ChanceNodes.

Super classes

rdecision::Edge -> rdecision::Arrow -> Reaction

Methods

Public methods

• Reaction$new()

• Reaction$grob()

• Reaction$modvars()

• Reaction$set_probability()

• Reaction$p()

• Reaction$set_cost()

• Reaction$cost()

• Reaction$set_benefit()

• Reaction$benefit()

• Reaction$clone()

Inherited methods

• rdecision::Edge$endpoints()
• rdecision::Edge$is_same_edge()
• rdecision::Edge$label()
• rdecision::Arrow$source()
• rdecision::Arrow$target()

---

Method new()

Create an object of type Reaction. A probability must be assigned to the edge. Optionally, a cost and a benefit may be associated with traversing the edge. A pay-off (benefit-cost) is sometimes used in edges of decision trees; the parametrization used here is more general.

Usage

Reaction$new(
  source_node,
  target_node,
  p = 0,
  cost = 0,
  benefit = 0,
  label = ""
)

Arguments

source_node

Chance node from which the reaction leaves.

target_node

Node which the reaction enters.

p

Conditional probability of traversing the reaction edge. At most one Reaction from each chance node may have this set to 'NA_real_', in which case it will be replaced by one minus the sum of conditional probabilities of the other reaction edges from the node.

cost

Cost associated with traversal of this edge (numeric or ModVar), not NA.

benefit

Benefit associated with traversal of the edge (numeric or ModVar), not NA.

label

Character string containing the reaction label.

Returns

A new Reaction object.

---

Method grob()

Creates a grid::grob for a reaction edge.

Usage

Reaction$grob(xs, ys, xt, yt, fs = 0.2)

Arguments

xs

x coordinate of source of edge, grid::unit object.

ys

y coordinate of source of edge, grid::unit object.

xt

x coordinate of target of edge, grid::unit object.

yt

y coordinate of target of edge, grid::unit object.

fs

Fraction of the edge which slopes.

Returns

A grid::grob containing the symbol and label.

---

Method modvars()

Find all the model variables of type ModVar that have been specified as values associated with this Action. Includes operands of these ModVars, if they are expressions.

Usage

Reaction$modvars()

Returns

A list of ModVars.

---

Method set_probability()

Set the probability associated with the reaction edge.

Usage

Reaction$set_probability(p)

Arguments

p

Conditional probability of traversing the reaction edge. Of type numeric or ModVar. If numeric, p must be in the range [0,1], or NA_real_. Note that setting p = NA will cause an error.

Returns

Updated Reaction object.

---

Method p()

Return the current value of the edge probability, i.e., the conditional probability of traversing the edge.

Usage

Reaction$p()

Returns

Numeric value in range [0,1].

---

Method set_cost()

Set the cost associated with the reaction edge.

Usage

Reaction$set_cost(c = 0)

Arguments

c

Cost associated with traversing the reaction edge. Of type numeric or ModVar.

Returns

Updated Reaction object.

---

Method cost()

Return the cost associated with traversing the edge.

Usage

Reaction$cost()

Returns

Cost.

---

Method set_benefit()

Set the benefit associated with the reaction edge.

Usage

Reaction$set_benefit(b = 0)

Arguments

b

Benefit associated with traversing the reaction edge. Of type numeric or ModVar.

Returns

Updated Action object.

---

Method benefit()

Return the benefit associated with traversing the edge.

Usage

Reaction$benefit()

Returns

Benefit.

---

Method clone()

The objects of this class are cloneable with this method.

Usage

Reaction$clone(deep = FALSE)

Arguments

deep

Whether to make a deep clone.

Author(s)

Andrew J. Sims [e-mail]

rdecision documentation built on April 3, 2025, 6:09 p.m.