我有溫度、降水資料框：
我想對以下型別的降水進行分類；
* 0: No precipitation
* 1: Snow
* 2: Mixed snow and rain
* 3: Rain
* 4: Drizzle
* 5: Freezing rain
* 6: Freezing drizzle
我嘗試了以下功能：
def func(x):
if smhi['Temperature'] < -8 and smhi['Precipitation'] > 1 : smhi['PreciCateg'] = '1'
elif smhi['Temperature'] < -2 and smhi['Precipitation'] > 1 : smhi['Temperature'] = '2'
elif smhi['Temperature'] < 30 and smhi['Precipitation'] >= 1 : smhi['PreciCateg'] = '3'
elif smhi['Temperature'] < 20 and smhi['Precipitation'] < 1 : smhi['Temperature'] = '4'
elif smhi['Temperature'] < 5 and smhi['Precipitation'] > 0.5 : smhi['PreciCateg'] = '5'
elif smhi['Temperature'] < 5 and smhi['Precipitation'] > 0.2 : smhi['Temperature'] = '6'
else: smhi['PreciCateg'] = '0'
smhi['PreciCateg'] = smhi.apply(func)
我得到：
ValueError：系列的真值不明確。使用 a.empty、a.bool()、a.item()、a.any() 或 a.all()。
我想我搞砸了分類的邏輯！？
uj5u.com熱心網友回復：
使用numpy.select：
import numpy as np
conditions = [smhi["Temperature"].lt(-8) & smhi["Precipitation"].gt(1),
smhi["Temperature"].lt(-2) & smhi["Precipitation"].gt(1),
smhi["Temperature"].lt(30) & smhi["Precipitation"].ge(1),
smhi["Temperature"].lt(20) & smhi["Precipitation"].lt(1),
smhi["Temperature"].lt(5) & smhi["Precipitation"].gt(0.5),
smhi["Temperature"].lt(5) & smhi["Precipitation"].gt(0.2)]
smhi["PreciCateg"] = np.select(conditions, [1,2,3,4,5,6], 0)
>>> smhi
Temperature Precipitation Wind Speed timestamp PreciCateg
0 -1.33 0.17 2.61 2017-1-1 0:00:00 4
1 -1.93 0.07 2.06 2017-1-1 1:00:00 4
2 -2.39 0.02 1.98 2017-1-1 2:00:00 4
3 -2.57 0.01 2.24 2017-1-1 3:00:00 4
4 -3.23 0.00 2.18 2017-1-1 4:00:00 4
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