r - 如何在R中完成行名称？

Question

我导入了一个看起来像这样的表:

df <- data.frame(study=c("A", "", "", "B", "C", ""), 
                 outcome=c("mortality", "mortality", "surgery", "mortality", "mortality", "surgery"), 
                 time.point=c("30d", "1y", "10d", "1y", "5y", "20d"))

第 2 和第 3 个结果属于研究 A，第 6 个结果属于研究 C。
在我的表格中，有各种类似的例子，每项研究的结果和时间点数量不规则。
如何为每一行指定一个好的名称，以表明研究和结果以及预测的时间点？
我希望它看起来像这样:

df_new <- data.frame(study=c("A", "", "", "B", "C", ""), 
                     outcome=c("mortality", "mortality", "surgery", "mortality", "mortality", "surgery"), 
                     time.point=c("30d", "1y", "10d", "1y", "5y", "20d"), 
                     rowname=c("A_mortality_30d", "A_mortality_1y", "A_surgery_10d", "B_mortality_1y", "C_mortality_5y", "C_surgery_20d"))

非常感谢!

Answer 1

这是一种将空字符串更改为 NA 的方法

library( data.table ); library( zoo )
#make it a data.table
setDT(df)
#set empty strings as NA
df[ study == "", study := NA_character_ ]
#create new column
df[, rowname := paste( zoo::na.locf( study), outcome, time.point, sep = "_")][]
#    study   outcome time.point         rowname
# 1:     A mortality        30d A_mortality_30d
# 2:  <NA> mortality         1y  A_mortality_1y
# 3:  <NA>   surgery        10d   A_surgery_10d
# 4:     B mortality         1y  B_mortality_1y
# 5:     C mortality         5y  C_mortality_5y
# 6:  <NA>   surgery        20d   C_surgery_20d