我如何df.fillna具有类别中值值

Question

我有一个大的数据集〜1MLN行，约有5000个缺席坐标（我想按“城市”类别填充中位数，但是Fillna正在奏效，如何实现它？

city = ['London', 'Paris', 'Vienna', 'Milan','London', 'Paris', 'Vienna', 'Milan']
lat = [51.510843900000005, 48.8671391, 48.204465500000005, 45.4787357, 51.510843900000005, 48.8671391, None,  None]
lng = [-0.1424476, 2.328075, 16.3686397, 9.1961308, -0.14244, 2.329, None, None]

data = pd.DataFrame(list(zip(city, lat, lng)),columns =['city', 'lat', 'lng'])

display(data['lat'].isna().sum())  # 2
display(data['lng'].isna().sum())  # 2

for city_name in set(data['city']):
    data[data['city'] == city_name ]['lat'].fillna(data[data['city'] == city_name ]['lat'].median())
    data[data['city'] == city_name ]['lng'].fillna(data[data['city'] == city_name ]['lng'].median())
    print(city_name, data[data['city'] == city_name ]['lat'].median(),data[data['city'] == city_name ]['lng'].median())

display(data['lat'].isna().sum())  # 2
display(data['lng'].isna().sum())  # 2 

Answer 1

您可以做：

data.groupby("city").transform(lambda x: x.fillna(x.median()))

首先 href =“ https://pandas.pydata.org/pandas-docs/stable/reference/reference/pandas.series.fillna.html” rel =“ nofollow noreferrer”> fillna> fillna> fillna 并计算中位数。 （您可以使用任何数学操作）