survival (version 3.5-8)

survfit: Create survival curves


This function creates survival curves from either a formula (e.g. the Kaplan-Meier), a previously fitted Cox model, or a previously fitted accelerated failure time model.


survfit(formula, ...)


An object of class survfit containing one or more survival curves.



either a formula or a previously fitted model


other arguments to the specific method


Terry Therneau


A survival curve is based on a tabulation of the number at risk and number of events at each unique death time. When time is a floating point number the definition of "unique" is subject to interpretation. The code uses factor() to define the set. For further details see the documentation for the appropriate method, i.e., ?survfit.formula or ?survfit.coxph.

A survfit object may contain a single curve, a set of curves (vector), a matrix of curves, or even a 3 way array: dim(fit) will reveal the dimensions. Predicted curves from a coxph model have one row for each stratum in the Cox model fit and one column for each specified covariate set. Curves from a multi-state model have one row for each stratum and a column for each state, the strata correspond to predictors on the right hand side of the equation. The default printing and plotting order for curves is by column, as with other matrices.

See Also

survfit.formula, survfit.coxph, survfit.object, print.survfit, plot.survfit, quantile.survfit, residuals.survfit, summary.survfit