python - 如何为列中存在的每个值导出变量

Question

您好，下面是我的数据集。

我需要根据每个形状计算体积。我如何应用公式而不使用太多 for 循环。我有超过 8-9 个这样的唯一值，我需要计算新派生变量中的体积

下面是数据框

输入:

  Type                   Len   wid    hig    dia
  cylinder                            165    42
  oval                   30    38     141 
  round                               131    48
  oval                   63    95     141
  cylinder                            120    42

输出:

  type                   Len   wid    hig    dia    vol
  cylinder                            165    42     238
  oval                   30    38     141           632
  round                               131    48     57
  oval                   63    95     141           200
  cylinder                            120    42     173

代码:

  def label_race (row):
     if Anomaly_1['Type'] == 'Cylindrical' :
        return (4/3*3.14*(Length/2)*(Width/2)*(Height/2))/1000
     if Anomaly_1['Type'] == 'Oval' :
        return (pi*(Diameter/2)^2*h)

Answer 1

您可以使用numpy.select :

m1 = Anomaly_1['Type'] == 'cylindrical'
m2 = Anomaly_1['Type'] == 'oval'
m3 = ... 

v1 = (4/3*3.14*(Anomaly_1['Len']/2)*(Anomaly_1['wid']/2)*(Anomaly_1['hig']/2))/1000
v2 = (np.pi*(Anomaly_1['dia']/2)**2*Anomaly_1['hig'])
v3 = ... 


Anomaly_1['vol'] = np.select([m1, m2, m3], [v1, v2, v3])

另一个具有自定义函数的解决方案，用于单独处理值:

def f(x):
    if x['Type'] == 'cylindrical':
        return (4/3*3.14*(x['Len']/2)*(x['wid']/2)*(x['hig']/2))/1000
    elif x['Type'] == 'oval':
        return (np.pi*(x['dia']/2)**2*x['hig'])


Anomaly_1['vol'] = Anomaly_1.apply(f, axis=1)