toInteger | R Documentation |
Translate group sequential design to integer events (survival designs) or sample size (other designs)
toInteger(x, ratio = x$ratio, roundUpFinal = TRUE)
x |
An object of class |
ratio |
Usually corresponds to experimental:control sample size ratio.
If an integer is provided, rounding is done to a multiple of
|
roundUpFinal |
Sample size is rounded up to a value of |
It is useful to explicitly provide the argument ratio
when a
gsDesign
object is input since gsDesign()
does not have a
ratio
in return.
ratio = 0, roundUpFinal = TRUE
will just round up the sample size
(also event count).
Rounding of event count targets is not impacted by ratio
.
Since x <- gsSurv(ratio = M)
returns a value for ratio
,
toInteger(x)
will round to a multiple of M + 1
if M
is a non-negative integer; otherwise, just rounding will occur.
The most common example would be if there is 1:1 randomization (2:1) and
the user wishes an even (multiple of 3) sample size, then toInteger()
will operate as expected.
To just round without concern for randomization ratio, set ratio = 0
.
If toInteger(x, ratio = 3)
, rounding for final sample size is done
to a multiple of 3 + 1 = 4; this could represent a 3:1 or 1:3
randomization ratio.
For 3:2 randomization, ratio = 4
would ensure rounding sample size
to a multiple of 5.
Output is an object of the same class as input x
; i.e.,
gsDesign
with integer vector for n.I
or gsSurv
with integer vector n.I
and integer total sample size. See details.
# The following code derives the group sequential design using the method
# of Lachin and Foulkes
x <- gsSurv(
k = 3, # 3 analyses
test.type = 4, # Non-binding futility bound 1 (no futility bound) and 4 are allowable
alpha = .025, # 1-sided Type I error
beta = .1, # Type II error (1 - power)
timing = c(0.45, 0.7), # Proportion of final planned events at interims
sfu = sfHSD, # Efficacy spending function
sfupar = -4, # Parameter for efficacy spending function
sfl = sfLDOF, # Futility spending function; not needed for test.type = 1
sflpar = 0, # Parameter for futility spending function
lambdaC = .001, # Exponential failure rate
hr = 0.3, # Assumed proportional hazard ratio (1 - vaccine efficacy = 1 - VE)
hr0 = 0.7, # Null hypothesis VE
eta = 5e-04, # Exponential dropout rate
gamma = 10, # Piecewise exponential enrollment rates
R = 16, # Time period durations for enrollment rates in gamma
T = 24, # Planned trial duration
minfup = 8, # Planned minimum follow-up
ratio = 3 # Randomization ratio (experimental:control)
)
# Convert sample size to multiple of ratio + 1 = 4, round event counts.
# Default is to round up both event count and sample size for final analysis
toInteger(x)
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