Description Usage Arguments Details Value Note Author(s) References See Also Examples
This function plots a conditional error function.
1 2 3 
typ 
type of test: 
fun 
a conditional error function 
dis 
a distortion method for a supplied conditional error function (see details): 
a2 
alpha2, the local level of the test after the second stage 
c 
the parameter c 
p1 
the pvalue p1 of the test after the first stage 
p2 
the pvalue p2 of the test after the second stage, defaults to 
x 
vector on which the conditional error function is plotted (should be relatively dense in [0,1]) 
add 
logical determining whether the bounds should be added to an existing plot (default) or a new plot should be opened 
xlim 
the x limits of the plot (default: 
ylim 
the y limits of the plot (default: 
plt.pt 
logical determining whether the point that the conditional error function is made to run through should be plotted or not (default: yes) 
plt.ptann 
logical determining whether the point that the conditional error function is made to run through should be annotated or not (default: yes) 
xlab 
a label for the x axis (default: no label) 
ylab 
a label for the y axis (default: no label) 
... 
arguments to be passed on to the underlying 
There are two alternative ways of specifying the desired conditional error function:
through a type typ
, and either a parameter (either a2
or c
) or a point (p1,p2)
, OR
through an initial conditional error function fun
, and possibly a distortion method dis
together with either the parameter a2
or a point (p1,p2)
Most people will only need the first of these two ways; the second leads to userdefined nonstandard tests.
If typ
is specified, a parameter a2
or c
or the point (p1,p2)
must be provided. In this case, plotCEF
plots the conditional error function of the chosen type with the given parameter or running through the given point.
If typ
is not specified, a conditional error function (i.e., a nonincreasing function defined on [0,1] with values in [0,1]) fun
must be provided. If no distortion method is selected (dis = NA
), fun
is plotted unchanged. Otherwise, the function is distorted using the chosen distortion method, either to match a desired second stage level a2
or to run through a specified point (p1,p2)
(one of which must be provided). Currently, two distortion methods are implemented:
dis = "pl"
, Power lines: For an initial function fun
, define f[r](x) = (f(x^r))^(1/r), r>0. Note that if fun
is a conditional error function of type "b"
(Bauer and Koehne, 1994), so is f[r].
dis = "pl"
, Vertical translation: The initial function fun
is shifted vertically.
See parconv
for more information on the two alternative parameterizations by alpha2 and c.
Internally, plotCEF
uses CEF
to compute the conditional error function that is to be plotted.
The function plotCEF
is invoked for its plotting effect; it returns no meaningful value.
Provide either typ
or fun
, not both! If typ
is provided, then also specify a2
, c
, or p1
(and possibly p2
). If fun
is provided, then also specify dis
and a2
, or dis
and p1
(and possibly p2
), or none of these.
Warning: Values of a2
close to 0 or 1 may not work for dis = "pl"
.
plt.pt
and plt.ptann
are not considered if p1 = NA
. plt.ptann
is not considered if plt.pt = FALSE
.
Note that in this implementation of adaptive twostage tests, early stopping bounds are not part of the conditional error function. Rather, they are specified separately (see also tsT
).
Marc Vandemeulebroecke
Bauer, P., Koehne, K. (1994). Evaluation of experiments with adaptive interim analyses. Biometrics 50, 10291041.
Lehmacher, W., Wassmer, G. (1999). Adaptive sample size calculations in group sequential trials. Biometrics 55, 12861290.
Vandemeulebroecke, M. (2006). An investigation of twostage tests. Statistica Sinica 16, 933951.
adaptTest
package description, parconv
, CEF
, tsT
1 2 3 4 5 6 7 8 9 10  ## Plot two conditional error functions of the LehmacherWassmer (1999) type:
## one to the local level alpha2=0.1, and one that runs through (p1,p2)=(0.3,0.7)
plotCEF(typ="l", a2=0.1, add=FALSE)
plotCEF(typ="l", p1=0.3, p2=0.7)
## Plot an explicitly defined conditional error function, and distort it
plotCEF(fun=function(x) ifelse(x<.5,(1x)^2, (1x)/2), add=FALSE)
plotCEF(fun=function(x) ifelse(x<.5,(1x)^2, (1x)/2), dis="pl", a2=.5)
foo < CEF(fun=function(x) ifelse(x<.5,(1x)^2, (1x)/2), dis="pl", a2=.5)
plotCEF(fun=foo, col="red")

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