cIndex: Concordance Index

Description Usage Arguments Details Value References Examples

View source: R/assessment.R


Compute concordance index (C-index or C-statistic) that allows weights for right-censored survival data. For example, Asano and Hirakawa (2017) proposed cure status weighting for cure models, which reduces to Harrell's C-index if weighs are all ones.


cIndex(time, event = NULL, risk_score, weight = NULL)



A numeric vector for observed times


A numeric vector for event indicators. If it is NULL (by default) or NA, event will be treated all as ones and the function will compute concordance index for uncensored survival data.


A numeric vector representing the risk scores of events.


A optional numeric vector for weights. If it is NULL (by default) or NA, equal weights will be used.


Let r_i, t_i, and δ_i denote the risk score, observed time, and event indicator of i-th subject. The pair of (t_i,δ_i) and (t_j,δ_j), where i<j, are defined to be comparable if t_i<t_j,δ_i=1 or t_i=t_j,δ_i=1,δ_j=0. In the context of survival analysis, the risk scores of a comparable pair are said to be concordant with the survival outcomes if r_i>r_j. The C-index is defined as the proportion of the concordant pairs among the comparable pairs. For comparable pair satisfying t_i<t_j,δ_i=1, we count 0.5 in the numerator of the concordance index for tied risk scores (r_i=r_j).


A named numeric vector that consists of


Asano, J., & Hirakawa, A. (2017). Assessing the prediction accuracy of a cure model for censored survival data with long-term survivors: Application to breast cancer data. Journal of Biopharmaceutical Statistics, 27(6), 918–932.

Harrell, F. E., Lee, K. L., & Mark, D. B. (1996). Multivariable prognostic models: Issues in developing models, evaluating assumptions and adequacy, and measuring and reducing errors. Statistics in medicine, 15(4), 361–387.


## See examples of function 'cox_cure'.

Example output

intsurv documentation built on Jan. 13, 2021, 3:46 p.m.