python - 将 pandas 数据框对齐为面板

Question

我有 12 个相同形状的数据框，用于 12 年的数据收集。我需要使用它作为面板来绘制时间序列轴(年)上的各个列值。因此，我认为我应该将这些框架对齐为面板。

1. 有人可以帮助我了解如何将数据框对齐为面板吗？
2. 这是准备沿第三维绘图的正确方法吗？

一些示例数据:

# for 2015
Grave Crimes    Cases Recorded  Mistake of Law fact
Abduction       725             3
Kidnapping      246             6
Arson           466             1
Mischief        436             1
House Breaking  12707           21
Grievous Hurt   1299            3

# for 2016
Grave Crimes    Cases Recorded  Mistake of Law fact
Abduction       738             4
Kidnapping      297             9
Arson           486             4
Mischief        394             1
House Breaking  10287           14
Grievous Hurt   1205            0

# for 2017
Grave Crimes    Cases Recorded  Mistake of Law fact
Abduction       647             2
Kidnapping      251             10
Arson           418             3
Mischief        424             0
House Breaking  8913            12
Grievous Hurt   1075            1

Answer 1

虽然面板允许添加维度，但分层索引是更常见的替代方案。例如，来自Python Data Science Handbook :

While Pandas does provide Panel and Panel4D objects that natively handle three-dimensional and four-dimensional data (see Aside: Panel Data), a far more common pattern in practice is to make use of hierarchical indexing (also known as multi-indexing) to incorporate multiple index levels within a single index. In this way, higher-dimensional data can be compactly represented within the familiar one-dimensional Series and two-dimensional DataFrame objects.

就你的情况

I have 12 dataframes of the same shape for 12 years of data collection. I need to use this as a panel to to plot the various column values across the time series axis (years).

假设您的 DataFrame 位于 df_2015、df_2016 和 df_2017 中。您可以执行以下操作:

df_2015['year'] = 2015
df_2016['year'] = 2016
df_2017['year'] = 2017
df = pd.concat([df_2015, df_2016, df_2017]).set_index(['Grave Crimes', 'year'])

例如，现在要获取“Abduction”的所有年份的数据，请使用

df[df.index.get_level_values(0) == 'Abduction']