Pocock {PwrGSD}

The Pocock Alpha Spending Function

Description

Stipulates alpha spending according to the Pocock spending function in the Lan-Demets boundary construction method. Its intended purpose is in constructing calls to GrpSeqBnds and PwrGSD.

Usage

Pocock()

Value

An object of class spending.function

type

Gives the spending function type, which is the character string "Pocock"

call

returns the call

Note

The print method returns the call by default

Author(s)

Grant Izmirlian

References

see references under PwrGSD

See Also

LanDemets, ObrienFleming, Pow, GrpSeqBnds, PwrGSD

Examples

## example 1: what is the result of calling a spending function

    ## A call to 'Pocock' just returns the call
    Pocock()

    ## but really its value is a list with a component named
    ## 'type' equal to "Pocock" and a component named
    ## 'call' equal to the call.
    names(Pocock)

    Pocock()$type

    Pocock()$call

## example 2: ...But the intended purpose of the spending functions is
## in constructing calls to 'GrpSeqBnds' and to 'PwrGSD':
     

    frac <- c(0.07614902,0.1135391,0.168252,0.2336901,0.3186155,
              0.4164776,0.5352199,0.670739,0.8246061,1)
    drift <- c(0.3836636,0.5117394,0.6918584,0.8657705,1.091984,
               1.311094,1.538582,1.818346,2.081775,2.345386)

    test <- GrpSeqBnds(frac=frac, EfficacyBoundary=LanDemets(alpha=0.05, spending=Pocock),
                       FutilityBoundary=LanDemets(alpha=0.10, spending=ObrienFleming),
                       drift=drift)