如何调整survminer::ggsurvplot轴标签与轴标题的间距？

问题场景 #

使用ggsurvplot_combine生成生存曲线时，y轴标题“Survival probability”与轴标签距离过近。直接用+ theme()修改会报错，因为ggsurvplot返回的不是普通ggplot对象，而是包含多个元素的列表。

可复现代码 #

require(survival)
require(survminer)
require(ggplot2)

set.seed(42)

a <- c(32,291,545, 44,3,792,352, 20,615,169, 61,156, 88,863,255, 33,132,5,
       63,8,964,831, 55,133, 12, 54,261,867, 17, 12,699,233,251,446, 43,223, 
       374, 75, 34, 69,120, 84,134,8,806,8, 48, 86,211, 2436, 61, 81, 87, 12, 
       838, 34, 17,141, 44,155,128,6, 29, 16, 16, 34,130,430,325, 41, 28, 53,
       32,291,545, 44,3,792,352, 20,615,169, 61,156, 88,863,255, 33,132,5,
       63,8,964,831, 55,133, 12, 54,261,867, 17, 12,699,233,251,446, 43,223,
       86, 54,3,630, 93,699, 25,746,6, 46, 22, 60,395,402,151, 26, 38,125, 
       75, 34, 69,120, 84,134,8,806,8, 48, 86,211, 2436, 61,
       191, 49, 59,6, 34, 56,2, 96, 422, 45, 70)

b <- sample(c("Alpha", "Beta", "Gamma"), length(a), replace = T)
c <- sample(0:1, length(a), replace = T)
df <- data.frame(a, b, c)

df$b <- factor(df$b, levels = c("Alpha", "Beta", "Gamma"))
avg <- survfit(Surv(time = a, event = c) ~ 1, data = df)
surv_b <- survfit(Surv(time = a, event = c) ~ b, data = df)
surv_comb <- list(surv_b, avg)

解决方法 #

ggsurvplot_combine返回的对象是一个列表，其中plot元素才是真正的ggplot绘图对象。我们可以提取这个元素后，再叠加theme()修改轴标题的间距：

# 生成绘图对象并赋值
p <- survminer::ggsurvplot_combine(
  surv_comb, 
  data = df,
  combine = TRUE,
  censor = FALSE,
  legend = "none",
  palette = c("orange", "steelblue", "seagreen", "black"),
  linetype = c(rep("solid",3), "dashed"),
)

# 修改y轴标题与标签的间距（这里调整右边距，数值可按需修改）
p$plot <- p$plot + theme(axis.title.y = element_text(margin = margin(r = 15)))

# 打印修改后的图表
print(p)

如果需要调整x轴标题（Time）的间距，把axis.title.y换成axis.title.x，并调整margin的t（上边距）参数即可，比如：

p$plot <- p$plot + theme(axis.title.x = element_text(margin = margin(t = 10)))

内容的提问来源于stack exchange，提问作者Reader 123