PocockSimonRandomizer-class: A Randomizer using the minimization method of Pocock and...

In bnaras/SRS: Subject Randomization System

Description

A randomizer implementing the minimization method of Pocock and Simon (1975). The definition here closely follows the description in the paper. Objects can be created by calls of the form new("PocockSimonRandomizer", expt, seed, tr.ratios, d.func, g.func, p.func). Arguments include a ClinicalExperiment object, a random number seed, the ratio of treatment counts, a function to use for computing imbalance for each treatment, a function to compute the overall imbalance, and a function that provides the probability allocation to address the imbalance.

Compute imbalances for each treatment assignment given a set of factor values

Compute the overall imbalance given individual imbalances

Randomize a subject given a subject id and the set of factor values

Return the last randomization performed

Usage

## S4 method for signature 'PocockSimonRandomizer'
show(object)

tr.assignments(x) <- value

## S4 replacement method for signature 'PocockSimonRandomizer'
tr.assignments(x) <- value

tr.assignments(x)

## S4 method for signature 'PocockSimonRandomizer'
tr.assignments(x)

stateTable(x)

## S4 method for signature 'PocockSimonRandomizer'
stateTable(x)

computeImbalances(object, factor.values)

## S4 method for signature 'PocockSimonRandomizer,character'
computeImbalances(object,
  factor.values)

computeOverallImbalance(object, imbalances)

## S4 method for signature 'PocockSimonRandomizer,matrix'
computeOverallImbalance(object,
  imbalances)

randomizeSubject(object) <- value

## S4 replacement method for signature 'PocockSimonRandomizer,list'
randomizeSubject(object) <- value

lastRandomization(object)

## S4 method for signature 'PocockSimonRandomizer'
lastRandomization(object)

Arguments

object	a PocockSimonRandomizer object
x	the randomizer
value	a named list of two items: subject.id, a character string, and factor values a vector of factor values
factor.values	the factor values
imbalances	the imbalances for each treatment
assignments	a conformable data frame of treatment assignments so far, with appropriately named variables

Value

a matrix of imbalances

the imbalance

a one-row data frame of the last treatment assignment

Slots

expt

a ClinicalExperiment object defining the experiment context

seed

A seed for the random number generator for reproducibility

stateTable

A matrix of counts indicating the marginal distribution of each factor level per treatment

tr.assignments

a data frame of treatment assignments so far

tr.ratios

the treatment arm ratio, for example 2:1 in a two treatment experiment

d.func

A function that computes the imbalance for each treatment

g.func

A function that computes the overall imbalance to be minimized

p.func

A function that computes the probability vector of treatment assignments

Examples

showClass("PocockSimonRandomizer")
expt <- ClinicalExperiment(number.of.factors = 2,
             number.of.factor.levels = c(2, 2))
randomizer <- new("PocockSimonRandomizer", expt, 1281L)
randomizeSubject(randomizer) <- list(subject.id = "Subject 1",
                                     factor.values = c("F1-1", "F2-2"))
randomizeSubject(randomizer) <- list(subject.id = "Subject 2",
                                     factor.values = c("F1-2", "F2-1"))
print(randomizer)

bnaras/SRS documentation built on May 12, 2019, 11:26 p.m.