如何从 R 中的行中删除最后的观察结果

Question

我有 dataframe 像这样：

df <- data.frame("date" = c('2018','2019','2020'), 
                 "var1" = c(21,15,47), 
                 "var2" = c(0.24,0.43,0.87), 
                 "var3" = c(0.23,0.35,NA), 
                 "var4" = c(0.64,NA,NA), 
                 "var5" = c(NA,NA,NA)
                 )

如何删除 NA 值之前每一行的最后两个观察值？ 变量date和var1应该是完整的。

df_want <- data.frame("date" = c('2018','2019','2020'), 
                 "var1" = c(21,15,47), 
                 "var2" = c(0.24,NA,NA), 
                 "var3" = c(NA,NA,NA), 
                 "var4" = c(NA,NA,NA), 
                 "var5" = c(NA,NA,NA)
)

Answer 1

一种方法是 for 循环：

for(i in seq(1,nrow(df))){
  y <- min(which(is.na(df[i,])))
  z <- max(y,which(colnames(df) == "var1") + 3)
  if (!is.infinite(y)) df[i,(z-2):ncol(df)] <- NA
}
df
  date var1 var2 var3 var4 var5
1 2018   21 0.24   NA   NA   NA
2 2019   15   NA   NA   NA   NA
3 2020   47   NA   NA   NA   NA