Reason Why a Survival Curve May Not Start from 100%

In Exploratory, you can create a survival curve using the Kaplan-Meier method. Normally, the survival period should begin at 100%, but in some cases, the curve may start at a value lower than 100%.

This issue indicates that there are data records where the start date and end date are the same (i.e., the event occurred at the start timing).

There is no problem in drawing such a survival curve, but if you want the curve to start at 100%, you can address this by excluding the data where the start and end dates are equal.

Exclude Data Where Start and End Dates Are Equal

If you want to exclude the data where the start and end dates are equal, go to the column header menu for the start date, choose “Filter”, “Not equal to” and “Date”.

When the date dialog appears, select “Column” as the value type, choose the end date column, and run the filter.

This allows you to remove the data where the start date and end date are the same.

If the start or end date contains missing values, please check the “Leave missing values” option.