python - pandas - 我如何从同一列上的数据框获得差异

Question

除了“值”列之外，我有 2 个相同的数据框，需要根据年+名称+月份列获取“值”列上的 2 个数据框的差异，并将其附加到数据集。

x1 = {
    "year": ["2018", "2018", "2018", "2018", "2018", "2018"],
    "name": ["abc", "xyz", "pqr", "stu", "hij", "efg"],
    "month": ["Jan-18", "Feb-18", "Mar-18", "Apr-18", "May-18", "Jun-18"],
    "value": [100, 200, 300, 400, 500, 600],
}
x2 = {
    "year": ["2019", "2019", "2019", "2019", "2019", "2019"],
    "name": ["abc", "xyz", "pqr", "stu", "hij", "efg"],
    "month": ["Jan-18", "Feb-18", "Mar-18", "Apr-18", "May-18", "Jun-18"],
    "value": [700, 300, 200, 500, 600, 100],
}
y1 = pd.DataFrame(x1).append(pd.DataFrame(x2), ignore_index=True)

print(y1)

结果应该像第 12 和 13 行

    year name   month  value
0   2018  abc  Jan-18    100
1   2018  xyz  Feb-18    200
...
...
6   2019  abc  Jan-18    700
7   2019  xyz  Feb-18    300
...
...
12   diff  abc  Jan-18    (700-100)
13   diff  xyz  Feb-18    (300-200)

Answer 1

在 sort_values 之后检查 groupby 和 diff

y2=y1.copy()
y2=y2.sort_values('year')
y2['value']=y2.groupby(['name','month']).value.diff()
y1=y1.append(y2.dropna().assign(year='diff'))
y1
    year name   month  value
0   2018  abc  Jan-18  100.0
1   2018  xyz  Feb-18  200.0
2   2018  pqr  Mar-18  300.0
3   2018  stu  Apr-18  400.0
4   2018  hij  May-18  500.0
5   2018  efg  Jun-18  600.0
6   2019  abc  Jan-18  700.0
7   2019  xyz  Feb-18  300.0
8   2019  pqr  Mar-18  200.0
9   2019  stu  Apr-18  500.0
10  2019  hij  May-18  600.0
11  2019  efg  Jun-18  100.0
6   diff  abc  Jan-18  600.0
7   diff  xyz  Feb-18  100.0
8   diff  pqr  Mar-18 -100.0
9   diff  stu  Apr-18  100.0
10  diff  hij  May-18  100.0
11  diff  efg  Jun-18 -500.0