typo in the qplot_survival function

[kippakers]

The last bit of code in the qplot_survival function reads:

ggplot(data=t.survframe, aes(colour=strata, group=strata)) + geom_step(aes(x=time, y=surv), direction="hv") + geom_ribbon(aes(x=time, ymax=upper, ymin=lower, fill=strata), directions="hv", linetype=0, alpha=0.25) + geom_point(data=subset(t.survframe, n.censor==1), aes(x=time, y=surv), shape=20) + geom_step(aes(x=time, y=upper), directions="hv", linetype=2, alpha=0.5) + geom_step(aes(x=time,y=lower), direction="hv", linetype=2, alpha=0.5)

But f.frame needs to replace t.survframe a few times. It should read:

ggplot(data=f.frame, aes(colour=strata, group=strata)) + geom_step(aes(x=time, y=surv), direction="hv") + geom_ribbon(aes(x=time, ymax=upper, ymin=lower, fill=strata), directions="hv", linetype=0, alpha=0.25) + geom_point(data=subset(f.frame, n.censor==1), aes(x=time, y=surv), shape=20) + geom_step(aes(x=time, y=upper), directions="hv", linetype=2, alpha=0.5) + geom_step(aes(x=time,y=lower), direction="hv", linetype=2, alpha=0.5)

Thanks for the code, by the way, it's great stuff!