risk: Logical scalar indicating whether to include a plot for the risk.
survival: Logical scalar indicating whether to include a plot for the survival.
xlab: Character string for the x axes of all plots.
ylab_risk: Character string for the y axis of the plot for the risk (if applicable).
ylab_surv: Character string for the y axis of the plot for the survival (if applicable).
ci_risk: Logical scalar specifying whether to include error bars for the 95% confidence intervals of the estimated risk under the natural course. This argument is only effective if the argument nsamples was set to a positive value in gformula_survival.