[英]Groupby column and find min and max of each group
I have the following dataset, 我有以下数据集,
Day Element Data_Value
6786 01-01 TMAX 112
9333 01-01 TMAX 101
9330 01-01 TMIN 60
11049 01-01 TMIN 0
6834 01-01 TMIN 25
11862 01-01 TMAX 113
1781 01-01 TMAX 115
11042 01-01 TMAX 105
1110 01-01 TMAX 111
651 01-01 TMIN 44
11350 01-01 TMIN 83
1798 01-02 TMAX 70
4975 01-02 TMAX 79
12774 01-02 TMIN 0
3977 01-02 TMIN 60
2485 01-02 TMAX 73
4888 01-02 TMIN 31
11836 01-02 TMIN 26
11368 01-02 TMAX 71
2483 01-02 TMIN 26
I want to group by the Day and then find the overall min of TMIN an the max of TMAX and put these in to a data frame, so I get an output like... 我想按天分组,然后找到TMIN的整体最小值和TMAX的最大值,然后将其放入数据帧,所以我得到了如下输出:
Day DayMin DayMax
01-01 0 115
01-02 0 79
I know I need to do, 我知道我需要做
df.groupby(by='Day')
but I am a stuck with the next step - should create columns to store the TMAX and TMIN values? 但我对下一步感到困惑-应该创建列来存储TMAX和TMIN值吗?
You can use a assign
+ abs
, followed by groupby
+ agg
: 您可以使用assign
+ abs
,然后使用groupby
+ agg
:
df = (df.assign(Data_Value=df['Data_Value'].abs())
.groupby(['Day'])['Data_Value'].agg([('Min' , 'min'), ('Max', 'max')])
.add_prefix('Day'))
df
DayMin DayMax
Day
01-01 0 115
01-02 0 79
Use 采用
In [5265]: def maxmin(x):
...: mx = x[x.Element == 'TMAX'].Data_Value.max()
...: mn = x[x.Element == 'TMIN'].Data_Value.min()
...: return pd.Series({'DayMin': mn, 'DayMax': mx})
...:
In [5266]: df.groupby('Day').apply(maxmin)
Out[5266]:
DayMax DayMin
Day
01-01 115 0
01-02 79 0
Also, 也,
In [5268]: df.groupby('Day').apply(maxmin).reset_index()
Out[5268]:
Day DayMax DayMin
0 01-01 115 0
1 01-02 79 0
Or, use query
instead of x[x.Element == 'TMAX']
as x.query("Element == 'TMAX'")
或者,使用query
代替x[x.Element == 'TMAX']
作为x.query("Element == 'TMAX'")
Create duplicate columns and find min and max using agg ie 创建重复的列并使用agg查找最小值和最大值
ndf = df.assign(DayMin = df['Data_Value'].abs(),DayMax=df['Data_Value'].abs()).groupby('Day')\
.agg({'DayMin':'min','DayMax':'max'})
DayMax DayMin Day 01-01 115 0 01-02 79 0
Incase you want both TMIN and TMAX then groupby(['Day','Element'])
如果您同时需要TMIN和TMAX,则进行groupby(['Day','Element'])
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