Special characters cannot be used for levels names of a categorical variable

[dnzmarcio]

Expected behavior

Drawing survival curves for any categorical variable.

Actual behavior

If the categorical variable has levels with characters '>', '<=' then survival curves are not drawn.

Steps to reproduce the problem

library(survival)
library(survminer)
data(lung)

age.c <- ifelse(lung$age < 50, "<= 50", "> 50")
lung2 <- data.frame(lung, age.c)

fit <- survfit(Surv(time, status) ~ age.c, data = lung2)
ggsurvplot(fit)

session_info()

Session info ------------------------------------------------------------------------------
 setting  value                       
 version  R version 3.3.2 (2016-10-31)
 system   i386, mingw32               
 ui       RStudio (1.0.44)            
 language (EN)                        
 collate  English_United States.1252  
 tz       America/Los_Angeles         
 date     2016-12-09                  

Packages ----------------------------------------------------------------------------------
 package    * version date       source        
 assertthat   0.1     2013-12-06 CRAN (R 3.3.2)
 colorspace   1.3-1   2016-11-18 CRAN (R 3.3.2)
 devtools   * 1.12.0  2016-06-24 CRAN (R 3.3.2)
 digest       0.6.10  2016-08-02 CRAN (R 3.3.2)
 ggplot2    * 2.2.0   2016-11-11 CRAN (R 3.3.2)
 gtable       0.2.0   2016-02-26 CRAN (R 3.3.2)
 lattice      0.20-34 2016-09-06 CRAN (R 3.3.2)
 lazyeval     0.2.0   2016-06-12 CRAN (R 3.3.2)
 magrittr     1.5     2014-11-22 CRAN (R 3.3.2)
 Matrix       1.2-7.1 2016-09-01 CRAN (R 3.3.2)
 memoise      1.0.0   2016-01-29 CRAN (R 3.3.2)
 munsell      0.4.3   2016-02-13 CRAN (R 3.3.2)
 plyr         1.8.4   2016-06-08 CRAN (R 3.3.2)
 Rcpp         0.12.8  2016-11-17 CRAN (R 3.3.2)
 scales       0.4.1   2016-11-09 CRAN (R 3.3.2)
 survival   * 2.40-1  2016-10-30 CRAN (R 3.3.2)
 survminer  * 0.2.3   2016-12-07 CRAN (R 3.3.2)
 tibble       1.2     2016-08-26 CRAN (R 3.3.2)
 withr        1.0.2   2016-06-20 CRAN (R 3.3.2)

[kassambara]

Hi @dnzmarcio,

To extract variable names used in survival::survfit(), the R code strsplit(strata, "=|,\\s+", perl=TRUE) was used in the surv_summary() function [survminer v0.2.3]. The splitting was done at any "=" symbol in the string, causing an error when special characters (=, <=, >=) are used for the levels of a categorical variable.

This has been now fixed by applying strsplit() only on the first instance of "=" symbol.

Thank you for pointing this out.

Best regards,
/A. Kassambara

[dnzmarcio]

Thank you.