向数据框添加一列，跳过粘贴 -

Question

我在合并时遇到问题。

我有 2 个数据框。

数据框 1：

structure(list(row = c(1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 
2, 3), col = c(1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 5, 5), 
    ltr = c("-", ".", ".", ".", ".", "Q", ".", "A", "R", "-", 
    ".", ".", ".", "T", ".")), row.names = c(NA, 15L), class = "data.frame")

数据框2：

structure(list(freq = c("0.76423", "0.76423", "0.03546", "0.43677", 
"0.76972", "0.45678", "0.23145", "0.56835", "0.23145")), row.names = c(NA, 
-9L), class = "data.frame")

我想将 freq 列从 dataframe2 复制到 dataframe1。 我想避免粘贴几行

如果 dataframe1 有 ltr = "-"（跳过该行和具有相同 col 值的后续行）

row col ltr freq
1    1   -   skip
2    1   .   skip
3    1   .   skip
1    2   .   0.76423

我尝试了循环，但没有成功。 结果应该是这样的

structure(list(row = c(1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 
2, 3), col = c(1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 5, 5), 
    ltr = c("-", ".", ".", ".", ".", "Q", ".", "A", "R", "-", 
    ".", ".", ".", "T", "."), freq = c("NA", "NA", "NA", "0.76423", 
    "0.76423", "0.03546", "0.43677", "0.76972", "0.45678", "NA", 
    "NA", "NA", "0.23145", "0.56835", "0.23145")), row.names = c(NA, 
15L), class = "data.frame")

谢谢！

Answer 1

一个选项是按“col”分组，通过检查“ltr”列中是否存在any“-”和第二个数据集中带有“freq”的replace TRUE 元素来创建一个逻辑列('df2')

library(dplyr)
df1 %>% 
   group_by(col) %>% 
   mutate(freq = if(any(ltr == "-")) NA else TRUE) %>% 
   ungroup %>% 
   mutate(freq = replace(freq, which(freq), df2$freq))
# A tibble: 15 x 4
#     row   col ltr   freq   
#   <dbl> <dbl> <chr> <chr>  
# 1     1     1 -     <NA>   
# 2     2     1 .     <NA>   
# 3     3     1 .     <NA>   
# 4     1     2 .     0.76423
# 5     2     2 .     0.76423
# 6     3     2 Q     0.03546
# 7     1     3 .     0.43677
# 8     2     3 A     0.76972
# 9     3     3 R     0.45678
#10     1     4 -     <NA>   
#11     2     4 .     <NA>   
#12     3     4 .     <NA>   
#13     1     5 .     0.23145
#14     2     5 T     0.56835
#15     3     5 .     0.23145

---

或者用data.table，将'data.frame'转换为'data.table'（setDT(df1)），按'col'分组，根据逻辑表达式找到行索引（.I），指定i 中的索引，并分配 (:=) 'df2' 中的 'freq' 值以在 'df1' 中创建 'freq' 列。默认情况下，i中没有的位置会被NA补上

library(data.table)
i1 <- setDT(df1)[, .I[all(ltr != "-")], col]$V1
df1[i1, freq := df2$freq]
df1
#    row col ltr    freq
# 1:   1   1   -    <NA>
# 2:   2   1   .    <NA>
# 3:   3   1   .    <NA>
# 4:   1   2   . 0.76423
# 5:   2   2   . 0.76423
# 6:   3   2   Q 0.03546
# 7:   1   3   . 0.43677
# 8:   2   3   A 0.76972
# 9:   3   3   R 0.45678
#10:   1   4   -    <NA>
#11:   2   4   .    <NA>
#12:   3   4   .    <NA>
#13:   1   5   . 0.23145
#14:   2   5   T 0.56835
#15:   3   5   . 0.23145