使用上面一行中的值在列中添加缺失值

Question

每周我都是一个不完整的分析数据集.看起来像:

df1 <- data.frame(var1 = c("a","","","b",""), 
             var2 = c("x","y","z","x","z"))

缺少一些var1值.数据集应该看起来像这样:

df2 <- data.frame(var1 = c("a","a","a","b","b"), 
             var2 = c("x","y","z","x","z"))

目前我使用Excel宏来执行此操作.但这使得分析自动化变得更加困难.从现在开始,我想在R中这样做.但我不知道该怎么做.

谢谢你的帮助.

评论后的问题更新

var2与我的问题无关.我唯一想做的就是.从df1到df2.

df1 <- data.frame(var1 = c("a","","","b",""))
df2 <- data.frame(var1 = c("a","a","a","b","b"))

Answer 1

这是通过使用行程编码(rle)及其反转来实现它的一种方法rle.inverse:

fillTheBlanks <- function(x, missing=""){
  rle <- rle(as.character(x))
  empty <- which(rle$value==missing)
  rle$values[empty] <- rle$value[empty-1] 
  inverse.rle(rle)
}

df1$var1 <- fillTheBlanks(df1$var1)

结果:

df1

  var1 var2
1    a    x
2    a    y
3    a    z
4    b    x
5    b    z

Answer 2

这是一个更简单的方法:

library(zoo)
df1$var1[df1$var1 == ""] <- NA
df1$var1 <- na.locf(df1$var1)

Answer 3

tidyr包具有fill()完成技巧的功能.

df1 <- data.frame(var1 = c("a","","","b",""))
fill(df1$var1)

Answer 4

这是另一种略短的方式,不会强迫角色:

Fill <- function(x,missing="")
{
  Log <- x != missing
  y <- x[Log]
  y[cumsum(Log)]
}

结果:

# For factor:
Fill(df1$var1)
[1] a a a b b
Levels:  a b

# For character:
Fill(as.character(df1$var1))
[1] "a" "a" "a" "b" "b"