如果我在以下数据帧中有一个异常列2019/2/1
:
date,type,ratio,2019/2/1
2019/1/1,food,0.4,0.3
2019/1/1,vegetables,0.2,0.6
2019/1/1,toy,0.1,0.5
如何将2019/2/1
垂直附加到ratio
?
预期结果如下:
date type ratio
0 2019/1/1 food 0.4
1 2019/1/1 vegetables 0.2
2 2019/1/1 toy 0.1
3 2019/2/1 food 0.3
4 2019/2/1 vegetables 0.6
5 2019/2/1 toy 0.5
第一个想法是rename
列ratio
在melt
:之前
df1 = (df.rename(columns={'ratio':'2019/1/1'})
.drop('date', 1)
.melt('type',value_name='ratio', var_name='date'))
print (df1)
type date ratio
0 food 2019/1/1 0.4
1 vegetables 2019/1/1 0.2
2 toy 2019/1/1 0.1
3 food 2019/2/1 0.3
4 vegetables 2019/2/1 0.6
5 toy 2019/2/1 0.5
另一种是在melt
:之后将datetime
从列替换为date
列
df['date'] = pd.to_datetime(df['date'])
df2 = df.melt(['date','type'],value_name='ratio')
df2['date'] = pd.to_datetime(df2.pop('variable'), errors='coerce').fillna(df2['date'])
print (df2)
date type ratio
0 2019-01-01 food 0.4
1 2019-01-01 vegetables 0.2
2 2019-01-01 toy 0.1
3 2019-02-01 food 0.3
4 2019-02-01 vegetables 0.6
5 2019-02-01 toy 0.5