pandas DataFrame applymap()函數

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pandas DataFrame的 applymap() 函數可以對DataFrame裡的每個值進行處理,然後返回一個新的DataFrame:

import pandas as pddf = pd.DataFrame({    ‘a‘: [1, 2, 3],    ‘b‘: [10, 20, 30],    ‘c‘: [5, 10, 15]})    def add_one(x):     return x + 1        print df.applymap(add_one)

   a   b   c0  2  11   61  3  21  112  4  31  16

一個栗子:

這裡有一組資料是10個學生的兩次考試成績,要求把成績轉換成ABCD等級:

轉換規則是:

90-100 -> A
80-89 -> B
70-79 -> C
60-69 -> D
0-59 -> F

grades_df = pd.DataFrame(    data={‘exam1‘: [43, 81, 78, 75, 89, 70, 91, 65, 98, 87],          ‘exam2‘: [24, 63, 56, 56, 67, 51, 79, 46, 72, 60]},    index=[‘Andre‘, ‘Barry‘, ‘Chris‘, ‘Dan‘, ‘Emilio‘,            ‘Fred‘, ‘Greta‘, ‘Humbert‘, ‘Ivan‘, ‘James‘])

def convert_to_letter(score):    if (score >= 90):        return ‘A‘    elif (score >= 80):        return ‘B‘    elif (score >= 70):        return ‘C‘    elif (score >= 60):        return ‘D‘    else:        return ‘F‘      def convert_grades(grades):    return grades.applymap(convert_to_letter)

print convert_grades(grades_df)

        exam1 exam2Andre       F     FBarry       B     DChris       C     FDan         C     FEmilio      B     DFred        C     FGreta       A     CHumbert     D     FIvan        A     CJames       B     D

 

pandas DataFrame applymap()函數