How to Create a Survival Curve

This post will take you from a variable that shows numeric values, such as the number of days to purchase a product:

To a state where you can visualize the probability of an event at a certain time interval, such as the proportion of people who have yet to purchase at each point in time. Survival curves are also known as Kaplan-Meier curves:

Requirements

You will need a numeric variable in your Data Sets tree. Numeric variables are represented by a "2" next to their name:

Method

1. From the toolbar, go to Calculation > Custom Code.
2. In the object inspector, go to Properties > R CODE and paste in the following code and click Calculate.

library(survival)
surv.days = Surv(days)
surv.fit = survfit(surv.days~1)
plot(surv.fit, main = "Kaplan-Meier estimate with 95% confidence bounds (86% of data)",
xlab = "Days since trial started",
xlim = c(0, 180),
ylab = "Survival function")
grid(20, 10, lwd = 2) 

In the code above, "surv.days = Surv(days)", days is the name of your numeric variable being used to create the density plot. This must be updated with the variable's name in your data set.

Next

How to Create a Density Plot Using R