任务，根据下一行添加新列 [英] Dask, add new column based on next row

问题描述

我有这个DASK数据框，最后一列是这个问题的重要信息：

Dask DataFrame Structure:
              asks[0].amount asks[1].amount asks[2].amount asks[3].amount asks[4].amount asks[5].amount asks[6].amount asks[7].amount asks[8].amount asks[9].amount asks[10].amount asks[11].amount asks[12].amount asks[13].amount asks[14].amount asks[15].amount asks[16].amount asks[17].amount asks[18].amount asks[19].amount asks[20].amount asks[21].amount asks[22].amount asks[23].amount asks[24].amount bids[0].amount bids[1].amount bids[2].amount bids[3].amount bids[4].amount bids[5].amount bids[6].amount bids[7].amount bids[8].amount bids[9].amount bids[10].amount bids[11].amount bids[12].amount bids[13].amount bids[14].amount bids[15].amount bids[16].amount bids[17].amount bids[18].amount bids[19].amount bids[20].amount bids[21].amount bids[22].amount bids[23].amount bids[24].amount currentPrice
npartitions=1                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
                     float64        float64        float64        float64        float64        float64        float64        float64        float64        float64         float64         float64         float64         float64         float64         float64         float64         float64         float64         float64         float64         float64         float64         float64         float64        float64        float64        float64        float64        float64        float64        float64        float64        float64        float64         float64         float64         float64         float64         float64         float64         float64         float64         float64         float64         float64         float64         float64         float64         float64      float64
                         ...            ...            ...            ...            ...            ...            ...            ...            ...            ...             ...             ...             ...             ...             ...             ...             ...             ...             ...             ...             ...             ...             ...             ...             ...            ...            ...            ...            ...            ...            ...            ...            ...            ...            ...             ...             ...             ...             ...             ...             ...             ...             ...             ...             ...             ...             ...             ...             ...             ...          ...

现在，我需要根据下一行‘CurrentPrice’添加一个新的列(名为SuctPrice)。例如：

row1: ask......, bids....., currentPrice(11), succPrice(12)
row2: ask......, bids....., currentPrice(12), succPrice(17)
row3: ask......, bids....., currentPrice(17), succPrice(.....)

如何才能获得此结果？数据帧非常大，因此我需要使用Dask

推荐答案

使用shift(-1)

Dasksshift的功能与 pandas shift的功能相同。也就是说，如果要使用下一行的值，则必须使用shift(-1)。

请记住，数据帧的最后一个值将是nan。

代码示例

import dask

# Create data
df = (dask.datasets.timeseries()
      .drop(columns=['id', 'name', 'y'])
      .rename(columns={'x': 'currentPrice'}))

# Assign `succPrice` equal to the next `currentPrice`
df = df.assign(succPrice=df['currentPrice'].shift(-1))

df.tail()

| timestamp           |   currentPrice |   succPrice |
|:--------------------|---------------:|------------:|
| 2000-01-30 23:59:55 |      -0.241575 |    0.65083  |
| 2000-01-30 23:59:56 |       0.65083  |    0.742577 |
| 2000-01-30 23:59:57 |       0.742577 |    0.313805 |
| 2000-01-30 23:59:58 |       0.313805 |    0.556262 |
| 2000-01-30 23:59:59 |       0.556262 |  nan        |

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