将列表列转换为数据框

Question

我在 spark 数据框中有一列列表。

+-----------------+
|features         |
+-----------------+
|[0,45,63,0,0,0,0]|
|[0,0,0,85,0,69,0]|
|[0,89,56,0,0,0,0]|
+-----------------+

如何将其转换为 spark 数据帧，其中列表中的每个元素都是数据帧中的一列？我们可以假设列表的大小相同。

例如，

+--------------------+
|c1|c2|c3|c4|c5|c6|c7|
+--------------------+
|0 |45|63|0 |0 |0 |0 |
|0 |0 |0 |85|0 |69|0 |
|0 |89|56|0 |0 |0 |0 |
+--------------------+

Answer 1

你所描述的实际上是VectorAssembler操作的反转。

您可以通过转换为中间 RDD 来实现，如下所示：

spark.version
# u'2.2.0'

# your data:
df.show(truncate=False)
# +-----------------+ 
# |        features | 
# +-----------------+
# |[0,45,63,0,0,0,0]|
# |[0,0,0,85,0,69,0]|
# |[0,89,56,0,0,0,0]|
# +-----------------+ 

dimensionality = 7
out = df.rdd.map(lambda x: [float(x[0][i]) for i in range(dimensionality)]).toDF(schema=['c'+str(i+1) for i in range(dimensionality)])
out.show()
# +---+----+----+----+---+----+---+ 
# | c1|  c2|  c3|  c4| c5|  c6| c7|
# +---+----+----+----+---+----+---+ 
# |0.0|45.0|63.0| 0.0|0.0| 0.0|0.0|
# |0.0| 0.0| 0.0|85.0|0.0|69.0|0.0| 
# |0.0|89.0|56.0| 0.0|0.0| 0.0|0.0| 
# +---+----+----+----+---+----+---+