Legend on survival plot

legend, plot, r, survival-analysis

Solution

You just need to specify a vector of colors the same length as the number of lines (i.e. groups) in your plot. You could do this as

N <- length(unique(group))
plot(kmsurvival1, xlab="Time",ylab="Survival Probability", mark.time = F,
col=1:N)
legend(
  "topright",
  legend=unique(group),
  col=1:N,
  horiz=FALSE,
  bty='n')

or you can manually specify the colors `col=c('black','blue','red')` (depending on how many colors you need).

From the example in `?plot.survfit`,

library(survival)
leukemia.surv <- survfit(Surv(time, status) ~ x, data = aml)
plot(leukemia.surv, lty = 2:3,col=3:4)
lLab <- gsub("x=","",names(leukemia.surv$strata))  ## legend labels
legend(
  "top",
  legend=lLab,
  col=3:4,
  lty=2:3,
  horiz=FALSE,
  bty='n')

Problem

Hi I am totally new to R. This is my first attempt at it. I am producing a survival plot broken down by age. I can't figure out how to specify colours for each age line and put it in a legend. Can anyone help? ``` require(survival) # not loaded by default although installed by default group <- age kmsurvival1 <- survfit(Surv(as.numeric(time),event) ~ group) plot(kmsurvival1, xlab="Time",ylab="Survival Probability", mark.time = F) ```

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