Description Usage Arguments Details Value Author(s) References See Also Examples
This function performs the BK-CUSUM procedure based on the
Biswas & Kalbfleisch (2008) CUSUM. For detection purposes, it is sufficient
to only determine the value of the chart at the times of failure. This can be
achieved by leaving ctimes
empty.
1 |
data |
and optionally additional covariates used for risk-adjustment. |
theta |
expected ln(hazard ratio) θ |
coxphmod |
(optional) a cox proportional hazards regression model as produced by
the function
|
cbaseh |
a function which returns the non risk-adjusted cumulative
baseline hazard H_0(t). If |
ctimes |
(optional) vector of construction times at which the value of the chart should be determined. When not specified, the chart is constructed at all failure times. |
h |
(optional) value of the control limit. The chart will only be constructed until the value of the control limit has been reached or surpassed. |
stoptime |
(optional) time after which the value of the chart should no longer be determined. Default = max(failure time). Useful when ctimes has not been specified. |
C |
(optional) a numeric value indicating how long after entering the study
patients should no longer influence the value of the chart. This is
equivalent to right-censoring every observation at time |
pb |
(optional) boolean indicating whether a progress bar should be shown. Default = FALSE |
The BK-CUSUM can be used to test the hypothesis of an instant change
of fixed size exp(θ)
in the subject specific hazard rate from h_i(t) to
h_i(t) exp(θ). The parameter C
can be used
to ignore information provided by subjects C time units after their entry
into the study.
The BK-CUSUM is constructed as:
G(t) = max_{0 <= k <= t} (θ N(k,t) - (e^θ -1) Λ(k,t))
with θ the ln(expected hazard ratio) and
N(k,t) = N(t)-N(k)
with N(t) the counting process of all failures at time t and
Λ(k,t) = Λ(t) - Λ(k)
the with Λ(t) the summed cumulative intensity of all subjects at time t.
An object of class "bkcusum" containing:
BK
: list containing
$time (times at which chart is constructed),
$value (value of the chart at corresponding times),
stopind
: indicator for whether the chart was stopped by the control limit
call
: the call used to obtain output
There are plot
and
runlength
methods for "bkcusum" objects.
Daniel Gomon
Biswas P. and Kalbfleisch J.D. (2008), A risk-adjusted CUSUM in continuous time based on the Cox Model, doi: 10.1002/sim.3216
plot.bkcusum
, runlength.bkcusum
Other qcchart:
bercusum()
,
cgrcusum()
,
funnelplot()
1 2 3 4 5 6 7 8 9 | require(survival)
tdat <- subset(surgerydat, Hosp_num == 14)
tcbaseh <- function(t) chaz_exp(t, lambda = 0.01)
varsanalysis <- c("age", "sex", "BMI")
exprfit <- as.formula(paste("Surv(survtime, censorid) ~" ,paste(varsanalysis, collapse='+')))
tcoxmod <- coxph(exprfit, data= surgerydat)
#Alternatively, cbaseh can be left empty when specifying coxphmod through coxph()
bk <- bkcusum(data = tdat, theta = log(2), coxphmod = tcoxmod, cbaseh = tcbaseh, pb = TRUE)
plot(bk)
|
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