python - 填充数据框中缺失的行

Question

我有一个如下所示的数据框

   Hair   Eye    Freq
1  Black Brown      32
2  Brown Brown      53
3    Red Brown      10
4  Blond Brown       3
5    Red  Blue      10
6  Blond  Blue      30
7  Black Hazel      10
8  Blond Hazel       5

上面的数据帧中4种头发颜色的频率Black, Brown, Red and Blond不同眼睛颜色都有记录Brown, Blue and Hazel 。但是，我想填写相应眼睛颜色缺失的头发颜色频率，以便生成如下数据框。如有任何帮助，我们将不胜感激。

   Hair   Eye    Freq
1  Black Brown      32
2  Brown Brown      53
3    Red Brown      10
4  Blond Brown       3
5  Black  Blue      0
6  Brown  Blue      0
7    Red  Blue      10
8  Blond  Blue      30
9  Black Hazel      10
10 Brown Hazel      0
11   Red Hazel      0
12 Blond Hazel      5

Answer 1

使用 expand.grid 创建一个包含头发和眼睛颜色组合的新表格。然后使用连接方法将df1的频率绑定(bind)到df2。最后删除 NA。

library('data.table')
hair <- c('Black', 'Brown', 'Red', 'Blond')  # hair colors
eye <- c('Brown', 'Blue', 'Hazel')           # eye colors
df2 <- expand.grid(Hair = hair, Eye = eye)   # data frame with combinations of eye and hair colors
setDT(df2)[df1, `:=` (Freq = i.Freq), on = .(Hair, Eye)]  # join df2 with df1 based `on = .(Hair, Eye)` and bind `Freq` from df1 to df2
df2[is.na(Freq), Freq := 0 ]                # remove NA with 0

输出:

df2
#     Hair   Eye Freq
# 1: Black Brown   32
# 2: Brown Brown   53
# 3:   Red Brown   10
# 4: Blond Brown    3
# 5: Black  Blue    0
# 6: Brown  Blue    0
# 7:   Red  Blue   10
# 8: Blond  Blue   30
# 9: Black Hazel   10
# 10: Brown Hazel    0
# 11:   Red Hazel    0
# 12: Blond Hazel    5

数据:

df1 <- fread('id   Hair   Eye    Freq
1  Black Brown      32
2  Brown Brown      53
3    Red Brown      10
4  Blond Brown       3
5    Red  Blue      10
6  Blond  Blue      30
7  Black Hazel      10
8  Blond Hazel       5')

df1[, id:=NULL]