Question

我正在尝试使用Choropleth绘制一些数据（尤其是来自GitHub（terrorism in EU countries的数据集）。

我有这样的东西：

year  country1  countr2 country3
1970  10        20      30  
1971  40        50      60    
1972  70        80      90

据我所知，应该有这样的内容：

year  country   value
1970  country1  10
1970  country2  20
1970  country3  30
1971  country1  40
1971  country2  50
1971  country3  60
1972  country1  70
1972  country2  80
1972  country3  90

我如何通过Pandas实现这一目标？这是解决问题的好方法吗？

非常感谢您。

Answer 1

这种任务只是熊猫的竹子：)

您只需要stack您的DataFrame：

>>> import pandas as pd
>>> # First you need to make `iyear` as index when reading csv to DataFrame.
>>> df = pd.read_csv('eu_terrorism_fatalities_by_country.csv', index_col=0)
>>> df.iloc[0:5, 0:3] # Take a look
       Belgium  Denmark  France
iyear                          
1970         0        0       0
1971         0        0       0
1972         0        0       1
1973         0        0       5
1974         0        0       3
>>> res = df.stack() # Just this simple :D
>>> res.head() # That's it.
iyear         
1970   Belgium    0
       Denmark    0
       France     0
       Germany    0
       Greece     2
dtype: int64

请注意，结果res是 MultiIndex Series ，以及一些后续内容：

>>> res.index.names = ['year', 'country']
>>> res.name = 'value'
>>> res.head()
year  country
1970  Belgium    0
      Denmark    0
      France     0
      Germany    0
      Greece     2
Name: value, dtype: int64
>>> res.to_csv('results.csv', header=True)

在results.csv文件中：

year,country,value
1970,Belgium,0
1970,Denmark,0
1970,France,0
... ...
2014,Portugal,0
2014,Spain,0
2014,United Kingdom,0

如果您想将MultiIndex Series res转换为DataFrame，只需关注reset_index并使用其args来控制行为，请遵循您的评论：

>>> flat = res.reset_index()
>>> flat.head()
   year  country  value
0  1970  Belgium      0
1  1970  Denmark      0
2  1970   France      0
3  1970  Germany      0
4  1970   Greece      2
>>> flat2 = res.reset_index(level=1)
>>> flat2.head()
      country  value
year                
1970  Belgium      0
1970  Denmark      0
1970   France      0
1970  Germany      0
1970   Greece      2

如何重塑熊猫中的数据以使用Choropleth进行绘图

1 个答案: