我有一个这样的数据框。
Date Daily Risk Score
0 2020-06-26 6.0
1 2020-06-27 6.0
2 2020-06-28 6.0
3 2020-06-29 6.0
4 2020-06-30 6.0
5 2020-07-01 6.0
6 2020-07-02 6.0
7 2020-07-03 6.0
8 2020-07-04 6.0
9 2020-07-05 6.0
10 2020-07-06 6.0
11 2020-07-07 6.0
12 2020-07-08 6.0
13 2020-07-09 6.0
14 2020-06-26 6.0
15 2020-06-27 6.0
16 2020-06-28 6.0
17 2020-06-29 6.0
18 2020-06-30 6.0
19 2020-07-01 6.0
20 2020-07-02 6.0
21 2020-07-03 6.0
22 2020-07-04 6.0
23 2020-07-05 6.0
24 2020-07-06 6.0
25 2020-07-07 6.0
26 2020-07-08 6.0
27 2020-07-09 6.0
我想取整个数据帧（超过50k个条目）中所有相似日期的平均值。如何遍历每个日期，然后在末尾创建一列以列出14个值（对应于每天的平均值）？
预期输出为：
Date Daily Risk Score Mean
0 2020-06-26 6.0 a
1 2020-06-27 6.0 b
2 2020-06-28 6.0 c
3 2020-06-29 6.0 ...
4 2020-06-30 6.0
5 2020-07-01 6.0
6 2020-07-02 6.0
7 2020-07-03 6.0
8 2020-07-04 6.0
9 2020-07-05 6.0
10 2020-07-06 6.0
11 2020-07-07 6.0
12 2020-07-08 6.0
13 2020-07-09 6.0
14 2020-06-26 6.0
15 2020-06-27 6.0
16 2020-06-28 6.0
17 2020-06-29 6.0
18 2020-06-30 6.0
19 2020-07-01 6.0
20 2020-07-02 6.0
21 2020-07-03 6.0
22 2020-07-04 6.0
23 2020-07-05 6.0
24 2020-07-06 6.0
25 2020-07-07 6.0
26 2020-07-08 6.0
27 2020-07-09 6.0
其中a表示6-26的所有每日风险评分的平均值。 B是6-27的平均值，以此类推。
答案 0 :(得分：2)
这是一种基于numpy的方法，使用view_as_windows，步长为3，滚动显示列值。使用这种方法，如果不存在整个窗口，则省略输出。
from skimage.util import view_as_windows
a = df['Value'].to_numpy()
# strided view of a with a step size of 3
w = view_as_windows(a, len(a)//3, step=3)
# missing values not present in strided view (incomplete window)
missing = a[w.size:]
prev_means = w.mean(0)
# construct new array with missing values and means of w
# if no missing values, the mean is kept
prev_means[:len(missing)] = a[w.size:]
means = np.vstack([w, prev_means]).mean(0)
# new df column
new_col = np.full(len(a), np.nan)
new_col[:len(means)] = means
df['means'] = new_col
print(df)
Value means
0 1 3.000000 # (1+4+2+5)/4
1 2 4.000000 # (2+5+3+6)/4
2 3 2.666667 # (3+1+4)/3
3 4 NaN
4 5 NaN
5 1 NaN
6 2 NaN
7 3 NaN
8 4 NaN
9 5 NaN
10 6 NaN
答案 1 :(得分：1)
您可以将np.r_与np.nanmean一起使用
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'interceptor' defined in com.example.InterceptorApplication: Bean instantiation via factory method failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [com.example.Interceptor]: Factory method 'interceptor' threw exception; nested exception is org.aspectj.lang.NoAspectBoundException: Exception while initializing com.example.Interceptor: java.lang.NoSuchMethodException: com.example.Interceptor.aspectOf()
at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:656) ~[spring-beans-5.2.3.RELEASE.jar:5.2.3.RELEASE]
at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:484) ~[spring-beans-5.2.3.RELEASE.jar:5.2.3.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1338) ~[spring-beans-5.2.3.RELEASE.jar:5.2.3.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1177) ~[spring-beans-5.2.3.RELEASE.jar:5.2.3.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:557) ~[spring-beans-5.2.3.RELEASE.jar:5.2.3.RELEASE]
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.3.RELEASE.jar:5.2.3.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.3.RELEASE.jar:5.2.3.RELEASE]
at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.2.3.RELEASE.jar:5.2.3.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.3.RELEASE.jar:5.2.3.RELEASE]
at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.3.RELEASE.jar:5.2.3.RELEASE]
at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:879) ~[spring-beans-5.2.3.RELEASE.jar:5.2.3.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:878) ~[spring-context-5.2.3.RELEASE.jar:5.2.3.RELEASE]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.2.3.RELEASE.jar:5.2.3.RELEASE]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.2.4.RELEASE.jar:2.2.4.RELEASE]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) ~[spring-boot-2.2.4.RELEASE.jar:2.2.4.RELEASE]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) ~[spring-boot-2.2.4.RELEASE.jar:2.2.4.RELEASE]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) ~[spring-boot-2.2.4.RELEASE.jar:2.2.4.RELEASE]
at org.springframework.boot.builder.SpringApplicationBuilder.run(SpringApplicationBuilder.java:140) [spring-boot-2.2.4.RELEASE.jar:2.2.4.RELEASE]
at com.example.InterceptorApplication.main(InterceptorApplication.java:27) [classes/:na]
def mean_window(arr, s):
l = len(arr)
fill_values = (s - l%s) if l%s else 0
return np.nanmean(np.r_[arr,[np.nan]*fill_values].reshape(-1,s),axis=0)
mean_window(df.Value.to_numpy, 3)
# array([3. , 4. , 2.66666667])
答案 2 :(得分：0)
df[::3]['Value'].mean()
这将得到您想要的，但是您也希望将其分配给一列，您希望结果如何？