一行数据行中其行距与行距之差3行

时间:2019-01-22 05:13:10

标签: python dataframe dask shift

我有一个CSV文件,它是通过以下代码作为dask数据帧导入的:

import dask.dataframe as dd
df = dd.read_csv("name and path of the file.csv")
df.head(10)

输出

+-----+------+-----+
|col1 | col2 | col3|
+-----+------+-----+    
|  A  |  2   |  4  |
+-----+------+-----+    
|  A  |  4   |  5  | 
+-----+------+-----+    
|  A  |  7   |  7  | 
+-----+------+-----+    
|  A  |  3   |  8  | 
+-----+------+-----+    
|  A  |  7   |  3  | 
+-----+------+-----+    
|  B  |  8   |  9  |
+-----+------+-----+    
|  B  |  10  |  10 | 
+-----+------+-----+    
|  B  |  8   |  9  |
+-----+------+-----+    
|  B  |  20  |  15 |
+-----+------+-----+

我要创建另一列col4,其中col1中的每个组分别包含col2[n+3]/col2-1

输出应为

   +-----+------+-----+-----+
   |col1 | col2 | col3| col4|
   +-----+------+-----+-----+    
   | A   |    2 |   4 |  0.5|  #(3/2-1)
   +-----+------+-----+-----+    
   | A   |    4 |   5 | 0.75| #(7/4-1)
   +-----+------+-----+-----+    
   | A   |    7 |   7 |  NA |
   +-----+------+-----+-----+    
   | A   |    3 |   8 |  NA |
   +-----+------+-----+-----+    
   | A   |    7 |   3 |  NA |
   +-----+------+-----+-----+    
   | B   |    8 |   9 | 1.5 |
   +-----+------+-----+-----+    
   | B   |   10 |  10 |  NA |
   +-----+------+-----+-----+    
   | B   |    8 |  9  |  NA |
   +-----+------+-----+-----+    
   | B   |   20 |  15 |  NA |
   +-----+------+-----+-----+

我们可以在熊猫上执行以下任务

df['col4'] = df.groupby('col1')['col2'].transform(lambda x: x.shift(-3)) / df['col2'] - 1

,但不能立即使用。任何帮助将不胜感激

1 个答案:

答案 0 :(得分:0)

在此PR:https://github.com/dask/dask/pull/1769中,diff方法现已添加到DataFrame和Series中。与熊猫一样。

此外,我只是要您在仅提供索引的地方使用diff

我想已经有一个用dask实现Shift()的任务了...。我已经提供了上面的链接...我希望它将回答您的问题

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