geom_km_ticks: Add Tick Marks to a Kaplan-Meier Survival Curve

Description

Adds tickmarks at the times when there are censored observations but no events.

Usage

geom_km_ticks(
  mapping = NULL,
  data = NULL,
  stat = "km_ticks",
  position = "identity",
  show.legend = NA,
  inherit.aes = TRUE,
  na.rm = TRUE,
  ...
)

Arguments

mapping

Set of aesthetic mappings created by aes(). If specified and inherit.aes = TRUE (the default), it is combined with the default mapping at the top level of the plot. You must supply mapping if there is no plot mapping.

data

The data to be displayed in this layer. There are three options:

If NULL, the default, the data is inherited from the plot data as specified in the call to ggplot().

A data.frame, or other object, will override the plot data. All objects will be fortified to produce a data frame. See fortify() for which variables will be created.

A function will be called with a single argument, the plot data. The return value must be a data.frame, and will be used as the layer data. A function can be created from a formula (e.g. ~ head(.x, 10)).

stat

The statistical transformation to use on the data for this layer, either as a ggproto Geom subclass or as a string naming the stat stripped of the stat_ prefix (e.g. "count" rather than "stat_count")

position

Position adjustment, either as a string naming the adjustment (e.g. "jitter" to use position_jitter), or the result of a call to a position adjustment function. Use the latter if you need to change the settings of the adjustment.

show.legend

logical. Should this layer be included in the legends? NA, the default, includes if any aesthetics are mapped. FALSE never includes, and TRUE always includes. It can also be a named logical vector to finely select the aesthetics to display.

inherit.aes

If FALSE, overrides the default aesthetics, rather than combining with them. This is most useful for helper functions that define both data and aesthetics and shouldn't inherit behaviour from the default plot specification, e.g. borders().

na.rm

If FALSE, the default, missing values are removed with a warning. If TRUE, missing values are silently removed.

...

Other arguments passed on to layer(). These are often aesthetics, used to set an aesthetic to a fixed value, like colour = "red" or size = 3. They may also be parameters to the paired geom/stat.

Aesthetics

geom_km_ticks() understands the following aesthetics (required aesthetics in bold):

x: the survival/censoring times, automatically mapped by stat_km_ticks().
y: the survival probability estimates, automatically mapped by stat_km_ticks().
alpha
color
shape
size
stroke
fill

Author

Michael Sachs (in ggkm), Samer Mouksassi (in ggquickeda).

Examples

Run this code

library(ggplot2)
sex <- rbinom(250, 1, .5)
df <- data.frame(
  time = exp(rnorm(250, mean = sex)),
  status = rbinom(250, 1, .75),
  sex = sex
)
ggplot(df, aes(time = time, status = status, color = factor(sex), group = factor(sex))) +
  geom_km() +
  geom_km_ticks(col = "black")