spark中的方法如何威胁向量汇编列?例如,如果我有经度和纬度列,是否更好地使用向量汇编程序组装它们然后将它放入我的模型中,或者如果我直接(单独)放置它们没有任何区别?
例1:
loc_assembler = VectorAssembler(inputCols=['long', 'lat'], outputCol='loc')
vector_assembler = VectorAssembler(inputCols=['loc', 'feature1', 'feature2'], outputCol='features')
lr = LinearRegression(maxIter=10, regParam=0.3, elasticNetParam=0.8)
pipeline = Pipeline(stages=[loc_assembler, vector_assembler, lr])
例2:
vector_assembler = VectorAssembler(inputCols=['long', 'lat', 'feature1', 'feature2'], outputCol='features')
lr = LinearRegression(maxIter=10, regParam=0.3, elasticNetParam=0.8)
pipeline = Pipeline(stages=[vector_assembler, lr])
有什么不同?哪一个更好?
没有任何区别只是因为在你的例子中,features
列的最终形式将是相同的,即在你的第一个例子中,loc
向量将被分解为它的各个组成部分。
这里是虚拟数据的简短演示(将线性回归部分放在一边,因为这不是讨论的必要条件):
spark.version
# u'2.3.1'
# dummy data:
df = spark.createDataFrame([[0, 33.3, -17.5, 10., 0.2],
[1, 40.4, -20.5, 12., 2.2],
[2, 28., -23.9, -2., -1.7],
[3, 29.5, -19.0, -0.5, -0.2],
[4, 32.8, -18.84, 1.5, 1.8]
],
["id","lat", "long", "other", "label"])
from pyspark.ml.feature import VectorAssembler
from pyspark.ml.pipeline import Pipeline
loc_assembler = VectorAssembler(inputCols=['long', 'lat'], outputCol='loc')
vector_assembler = VectorAssembler(inputCols=['loc', 'other'], outputCol='features')
pipeline = Pipeline(stages=[loc_assembler, vector_assembler])
model = pipeline.fit(df)
model.transform(df).show()
结果是:
+---+----+------+-----+-----+-------------+-----------------+
| id| lat| long|other|label| loc| features|
+---+----+------+-----+-----+-------------+-----------------+
| 0|33.3| -17.5| 10.0| 0.2| [-17.5,33.3]|[-17.5,33.3,10.0]|
| 1|40.4| -20.5| 12.0| 2.2| [-20.5,40.4]|[-20.5,40.4,12.0]|
| 2|28.0| -23.9| -2.0| -1.7| [-23.9,28.0]|[-23.9,28.0,-2.0]|
| 3|29.5| -19.0| -0.5| -0.2| [-19.0,29.5]|[-19.0,29.5,-0.5]|
| 4|32.8|-18.84| 1.5| 1.8|[-18.84,32.8]|[-18.84,32.8,1.5]|
+---+----+------+-----+-----+-------------+-----------------+
即features
列可以说与你的第二个例子(这里没有显示)相同,你不使用中间组装特征loc
...