Question

我有以下数据帧df1。我如何保存最后一次出现的w.之后的列值，例如对于id 6来说最后一次出现的w是在t8时，因此，我想保存出现的值在t9处以及在新数据帧中最后一个w的位置。

输入：

 id t1 t2 t3 t4 t5 t6 t7 t6 t8 t9
  1  s  s  s  w  r  r  t  t  w  s
  2  s  s  s  o  o  w  t  t  o  s
  3  s  s  s  o  w  w  t  t  o  s
  4  s  s  s  o  o  w  t  t  o  s
  5  w  s  s  s  s  s  w  w  s  s
  6  s  s  s  w  t  t  w  w  w  s

输出：

 id t1 t2 t3 t4 t5 t6 t7 t6 t8 t9
  1                          w  s
  2                 w  t  t  o  s
  3                 w  t  t  o  s
  4                 w  t  t  o  s
  5                       w  s  s
  6                          w  s

样本数据：

df1<-structure(list(id=c(1,2,3,4,5,6), t1=c("s","s","s","s","w","s"), t2=c("s","s","s","s","s","s"),t3 = c("s","s","s","s","s","s"),
                    t4 = c("w","o","o","o","s","w"), t5 = c("r","o","w","o","s","t"), t6 = c("r","w","w","w","s","t"),
                    t7 = c("t","t","t","t","w","w"),t6 = c("t","t","t","t","w","w"), t8 = c("w","o","o","o","s","w"), t9=c("s","s","s","s","s","s")), row.names = c(NA, 6L), class = "data.frame")

Answer 1

您可以逐行使用apply：

df1[-1] <- t(apply(df1[-1], 1, function(x) {
  ind <- max(which(x == 'w'))
  x[seq_len(ind - 1)] <- ''
  x
}))
df1

#  id t1 t2 t3 t4 t5 t6 t7 t6 t8 t9
#1  1                          w  s
#2  2                 w  t  t  o  s
#3  3                 w  t  t  o  s
#4  4                 w  t  t  o  s
#5  5                       w  s  s
#6  6                          w  s

max(which(x == 'w'))返回该行中最后一次出现的'w'的索引。

另一种选择是创建需要替换的行和列值矩阵。我们可以将max.col与ties.method = 'last'一起使用，这将为您提供最后一次出现的'w'的索引每一行。现在，我们需要为cols中的每个值创建一个从2到该数字的序列，以创建可用于替换空白值的矩阵。

cols <- max.col(df1[-1] == 'w', ties.method = 'last')
mat <- do.call(rbind, Map(function(x, y) cbind(x, seq(y)[-1]), 1:nrow(df1), cols))
df1[mat] <- ''

如果满足条件，将值保持在行中

1 个答案: