pandas自定义函数

电玩女神 2023-06-19 13:26 10阅读 0赞

1.  sort\_values和reset\_index
    
        new_titanic_survival = titanic_survival.sort_values("Age",ascending=False)
        print (new_titanic_survival[0:10])
        titanic_reindexed = new_titanic_survival.reset_index(drop=True)
        print(titanic_reindexed.iloc[0:10])
    
    运行结果：  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg_size_16_color_FFFFFF_t_70]
2.  自定义函数
    
        # This function returns the hundredth item from a series
        def hundredth_row(column):
            # Extract the hundredth item
            hundredth_item = column.iloc[99]
            return hundredth_item
        
        # Return the hundredth item from each column
        hundredth_row = titanic_survival.apply(hundredth_row)
        print (hundredth_row)
    
    运行结果：  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg_size_16_color_FFFFFF_t_70 1]
3.  非0行个数
    
        def not_null_count(column):
            column_null = pd.isnull(column)
            null = column[column_null]
            return len(null)
        
        column_null_count = titanic_survival.apply(not_null_count)
        print (column_null_count)
    
    运行结果：  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg_size_16_color_FFFFFF_t_70 2]
4.  练习
    
        #By passing in the axis=1 argument, we can use the DataFrame.apply() method to iterate over rows instead of columns.
        def which_class(row):
            pclass = row['Pclass']
            if pd.isnull(pclass):
                return "Unknown"
            elif pclass == 1:
                return "First Class"
            elif pclass == 2:
                return "Second Class"
            elif pclass == 3:
                return "Third Class"
        
        classes = titanic_survival.apply(which_class, axis=1)
        print (classes)
    
    运行结果：  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg_size_16_color_FFFFFF_t_70 3]
5.  连续值离散化
    
        def is_minor(row):
            if row["Age"] < 18:
                return True
            else:
                return False
        
        minors = titanic_survival.apply(is_minor, axis=1)
        #print minors
        
        def generate_age_label(row):
            age = row["Age"]
            if pd.isnull(age):
                return "unknown"
            elif age < 18:
                return "minor"
            else:
                return "adult"
        
        age_labels = titanic_survival.apply(generate_age_label, axis=1)
        print (age_labels)
    
    运行结果：  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg_size_16_color_FFFFFF_t_70 4]
6.  添加列
    
        titanic_survival['age_labels'] = age_labels
        age_group_survival = titanic_survival.pivot_table(index="age_labels", values="Survived")
        print (age_group_survival)
    
    运行结果：  
    ![在这里插入图片描述][20191206195813539.png]

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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20191206194556434.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg_size_16_color_FFFFFF_t_70 3]: https://img-blog.csdnimg.cn/20191206194923956.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg_size_16_color_FFFFFF_t_70 4]: https://img-blog.csdnimg.cn/20191206195613241.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjI2MDEwMg==,size_16,color_FFFFFF,t_70
[20191206195813539.png]: https://img-blog.csdnimg.cn/20191206195813539.png