计算季度的衰退和复苏

问题描述

给定这个数据框

   GDP quarter
0  250  2015q1
1  260  2015q1
2  250  2015q3
3  240  2015q4
4  250  2016q1
5  260  2016q2

我如何确定哪些季度是衰退，哪些季度是复苏?

How can I figure out what quarters are recessions and what quarters are recoveries?

经济衰退是指 GDP 连续两个季度下降

A Recession is when GDP is decreasing two quarters in a row

复苏是指 GDP 下降，但现在正在上升.

A Recovery is when GDP was decreasing, but is now on the rise.

推荐答案

这里需要用到Series.shift函数

Here you need to use the Series.shift function

由于您的数据不容易复制，我将创建自己的示例数据.

Since your data is not easily copypastable, I'll just create my own example data.

df = pd.DataFrame({"quarter":["2015q1", "2015q1", "2015q3", "2015q4", "2016q1", "2016q2"], "GDP": [250, 260, 250, 240, 250, 260]}
df['Last_GDP'] = df.GDP.shift(1)
df['Increase'] = df.GDP > df.Last_GDP
df['Last_Increase'] = df.Increase.shift(1)
df.ix[(~df.Last_Increase.fillna(False) & ~df.Increase), 'Re-x'] = "Recession"
df.ix[(~df.Last_Increase.fillna(False) & df.Increase), 'Re-x'] = "Recovery"
df.ix[df.Last_Increase.isnull(), 'Re-x'] = "Unknown"

   GDP quarter  Last_GDP Increase Last_Increase       Re-x
0  250  2015q1       NaN    False           NaN    Unknown
1  260  2015q1     250.0     True         False   Recovery
2  250  2015q3     260.0    False          True        NaN
3  240  2015q4     250.0    False         False  Recession
4  250  2016q1     240.0     True         False   Recovery
5  260  2016q2     250.0     True          True        NaN

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