Separate 2 groups in Cox regression

Instalation

if (!require("BiocManager")) {
    install.packages("BiocManager")
}
BiocManager::install("glmSparseNet")

Required Packages

library(futile.logger)
library(ggplot2)
library(glmSparseNet)
library(survival)

# Some general options for futile.logger the debugging package
flog.layout(layout.format("[~l] ~m"))
options("glmSparseNet.show_message" = FALSE)
# Setting ggplot2 default theme as minimal
theme_set(ggplot2::theme_minimal())

Prepare data

data("cancer", package = "survival")
xdata <- survival::ovarian[, c("age", "resid.ds")]
ydata <- data.frame(
    time = survival::ovarian$futime,
    status = survival::ovarian$fustat
)

Separate using age as co-variate

(group cutoff is median calculated relative risk)

resAge <- separate2GroupsCox(c(age = 1, 0), xdata, ydata)

Kaplan-Meier survival results

## Call: survfit(formula = survival::Surv(time, status) ~ group, data = prognosticIndexDf)
## 
##                n events median 0.95LCL 0.95UCL
## Low risk - 1  13      4     NA     638      NA
## High risk - 1 13      8    464     268      NA

Plot

A individual is attributed to low-risk group if its calculated relative risk (using Cox Proportional model) is below or equal the median risk.

The opposite for the high-risk groups, populated with individuals above the median relative-risk.

Separate using age as co-variate (group cutoff is 40% - 60%)

resAge4060 <-
    separate2GroupsCox(c(age = 1, 0),
        xdata,
        ydata,
        probs = c(.4, .6)
    )

Kaplan-Meier survival results

## Call: survfit(formula = survival::Surv(time, status) ~ group, data = prognosticIndexDf)
## 
##                n events median 0.95LCL 0.95UCL
## Low risk - 1  11      3     NA     563      NA
## High risk - 1 10      7    359     156      NA

Plot

A individual is attributed to low-risk group if its calculated relative risk (using Cox Proportional model) is below the median risk.

The opposite for the high-risk groups, populated with individuals above the median relative-risk.

Separate using age as co-variate (group cutoff is 60% - 40%)

This is a special case where you want to use a cutoff that includes some sample on both high and low risks groups.

resAge6040 <- separate2GroupsCox(
    chosenBetas = c(age = 1, 0),
    xdata,
    ydata,
    probs = c(.6, .4),
    stopWhenOverlap = FALSE
)
## Warning in buildPrognosticIndexDataFrame(ydata, probs, stopWhenOverlap, : The cutoff values given to the function allow for some over samples in both groups, with:
##   high risk size (15) + low risk size (16) not equal to xdata/ydata rows (31 != 26)
## 
## We are continuing with execution as parameter `stopWhenOverlap` is FALSE.
##   note: This adds duplicate samples to ydata and xdata xdata

Kaplan-Meier survival results

## Kaplan-Meier results
## Call: survfit(formula = survival::Surv(time, status) ~ group, data = prognosticIndexDf)
## 
##                n events median 0.95LCL 0.95UCL
## Low risk - 1  16      5     NA     638      NA
## High risk - 1 15      9    475     353      NA

Plot

A individual is attributed to low-risk group if its calculated relative risk (using Cox Proportional model) is below the median risk.

The opposite for the high-risk groups, populated with individuals above the median relative-risk.

Session Info

sessionInfo()
## R version 4.5.2 (2025-10-31)
## Platform: x86_64-pc-linux-gnu
## Running under: Ubuntu 24.04.4 LTS
## 
## Matrix products: default
## BLAS:   /usr/lib/x86_64-linux-gnu/openblas-pthread/libblas.so.3 
## LAPACK: /usr/lib/x86_64-linux-gnu/openblas-pthread/libopenblasp-r0.3.26.so;  LAPACK version 3.12.0
## 
## locale:
##  [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C              
##  [3] LC_TIME=en_US.UTF-8        LC_COLLATE=C              
##  [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8   
##  [7] LC_PAPER=en_US.UTF-8       LC_NAME=C                 
##  [9] LC_ADDRESS=C               LC_TELEPHONE=C            
## [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       
## 
## time zone: Etc/UTC
## tzcode source: system (glibc)
## 
## attached base packages:
##  [1] grid      parallel  stats4    stats     graphics  grDevices utils    
##  [8] datasets  methods   base     
## 
## other attached packages:
##  [1] glmnet_4.1-10               VennDiagram_1.8.2          
##  [3] reshape2_1.4.5              forcats_1.0.1              
##  [5] Matrix_1.7-4                glmSparseNet_1.29.0        
##  [7] TCGAutils_1.31.4            curatedTCGAData_1.33.1     
##  [9] MultiAssayExperiment_1.37.2 SummarizedExperiment_1.41.1
## [11] Biobase_2.71.0              GenomicRanges_1.63.1       
## [13] Seqinfo_1.1.0               IRanges_2.45.0             
## [15] S4Vectors_0.49.0            BiocGenerics_0.57.0        
## [17] generics_0.1.4              MatrixGenerics_1.23.0      
## [19] matrixStats_1.5.0           futile.logger_1.4.9        
## [21] survival_3.8-6              ggplot2_4.0.2              
## [23] dplyr_1.2.0                 BiocStyle_2.39.0           
## 
## loaded via a namespace (and not attached):
##   [1] RColorBrewer_1.1-3        sys_3.4.3                
##   [3] jsonlite_2.0.0            shape_1.4.6.1            
##   [5] magrittr_2.0.4            GenomicFeatures_1.63.1   
##   [7] farver_2.1.2              rmarkdown_2.30           
##   [9] BiocIO_1.21.0             vctrs_0.7.1              
##  [11] memoise_2.0.1             Rsamtools_2.27.1         
##  [13] RCurl_1.98-1.17           rstatix_0.7.3            
##  [15] htmltools_0.5.9           S4Arrays_1.11.1          
##  [17] BiocBaseUtils_1.13.0      progress_1.2.3           
##  [19] AnnotationHub_4.1.0       lambda.r_1.2.4           
##  [21] curl_7.0.0                broom_1.0.12             
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##  [45] labeling_0.4.3            httr_1.4.8               
##  [47] abind_1.4-8               compiler_4.5.2           
##  [49] bit64_4.6.0-1             withr_3.0.2              
##  [51] S7_0.2.1                  backports_1.5.0          
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##  [73] BiocVersion_3.23.1        foreach_1.5.2            
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##  [77] splines_4.5.2             BiocFileCache_3.1.0      
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##  [93] cigarillo_1.1.0           tibble_3.3.1             
##  [95] BiocManager_1.30.27       cli_3.6.5                
##  [97] jquerylib_0.1.4           Rcpp_1.1.1               
##  [99] GenomeInfoDb_1.47.2       GenomicDataCommons_1.35.1
## [101] dbplyr_2.5.2              png_0.1-9                
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