Description Usage Arguments Details Value Author(s) References See Also Examples
This function generates weighted predictiveness curve estimates and/or confident bands using parametric approach.
1 | cox.wpc.est(event, censor, marker, cutoff, quantile)
|
event |
This is the survival time. It is a positive numerical vector with no missing values. |
censor |
This specifies censor information. It is a vector, with 1 indicating an event and 0 indicating right censored. No missing values are allowed. |
marker |
This is the biomarker information (or other interesting variables). It is numerical with no missing values. |
cutoff |
This is to define the time cutoff. |
quantile |
This specifies the quantile of the confident band. Default is 0.95, 95% Confident band will be generated. |
The Cox proportional hazard model with a single biomarker will be used to derive and draw the predictiveness curve for parametric WPC. The relationship could be written in the form of the survival function as follows: S(t)=[S_0(t)]^{exp{xβ}}, where S(t) is survival function, S_0(t) is baseline survivor function, and x is the biomarker of interest. The effect of the biomarker is expressed by the exp(xβ) term and quantified as a shift from the baseline survival S_0(t). Because S_0(t) is always between 0 and 1, a positive coefficient β will decrease the survival function with increasing biomarker values; a negative coefficient β will increase the survival function with decreasing biomarker values. For any given time t, the baseline survival function S_0(t) could be estimated. Therefore, with a fixed coefficient estimate and fixed time, we could do such prediction for a range of x values by fitting x values into the formula earlier and then connect the predictions derived from the smallest x value to the largest x value. That will form the predictiveness curve for that particular time point.
A list with components:
x |
a vector of biomarker values. |
s |
A vector of survival rate estimates for each biomarker value. |
lb |
A vector of confident lower bands |
ub |
A vector of confident upper band |
Hui Yang huiy@amgen.com, Rui Tang rui_tang@vrtx.com and Jing Huang jinghuang0@gmail.com
Yang H., Tang R., Hale M. and Huang J. (2016) A visualization method measuring the performance of biomarkers for guiding treatment decisions Pharmaceutical Statistics, 15(2), 1539-1612
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