R平滑生存曲线力开始和结束

Question

我想平滑一条生存曲线，使其没有 'steps'。我正在尝试使用以下数据：

library(ggplot2)
df1<-data.frame(y=c(1,0.99,0.97,0.95,0.94,0.94,0.82,0.72,0.58,0.34,0.20,0.12,0.11,0), 
time=c(3,4,7,8,10,11,13,14,15,17,20,22,23,24))
ggplot(df1, aes(time,y)) + geom_point() +
  geom_smooth(method = "gam", formula = y ~ poly(x, 2),se=F)

但是平滑线的起点高于 1，终点低于 0（这对于生存图来说是不可能的）。怎么能适合这样的一行：

行开始于 y,x 值= 1,0
结束于 y,x 值=0,24
总是单调递减函数

Answer 1

将 ylim(0:1) 添加到您的代码中：

ggplot(df1, aes(time,y)) + 
  geom_point() +
  ylim(0:1) +
  geom_smooth(method = "gam", formula = y ~ poly(x, 2),se=F)

Answer 2

根据 IRTFM 评论，我找到了答案，代码如下：

library(cobs)
library(ggplot2)
df1<-data.frame(y=c(1,0.99,0.97,0.95,0.94,0.94,0.82,0.72,0.58,0.34,0.20,0.12,0.11,0), 
            time=c(3,4,7,8,10,11,13,14,15,17,20,22,23,24))

con2 <- rbind(c( 1,min(df1$time),1), 
          c(-1,max(df1$time),0)) 

Sb1 <- cobs(df1$time,df1$y, constraint="decrease", nknots=4,pointwise= con2,
        degree = 2)

summary(Sb1)
plot(Sb1, main='Survival Curve')

谢谢

R平滑生存曲线力开始和结束

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