"PySpark MLlib逻辑回归多标签问题"

Question

我试图创建一个logisticRegressionWithGD，但是它得到的错误是

org.apache.spark.SparkException: Input validation failed.

如果我给它二进制输入（0,1而不是0,1,2），它确实成功了。在

输入示例：

^{pr2}$

代码： model = LogisticRegressionWithSGD.train(parsed_data)

spark中的Logistic回归模型应该只用于二元分类吗？在

Answer 1

虽然从文档中看不清楚（您必须深入研究source code才能实现它），但是LogisticRegressionWithSGD只适用于二进制数据；对于多项式回归，您应该使用LogisticRegressionWithLBFGS：

 from pyspark.mllib.classification import LogisticRegressionWithLBFGS, LogisticRegressionModel, LogisticRegressionWithSGD
 from pyspark.mllib.regression import LabeledPoint
 parsed_data = [LabeledPoint(0.0, [4.6,3.6,1.0,0.2]),
                LabeledPoint(0.0, [5.7,4.4,1.5,0.4]),
                LabeledPoint(1.0, [6.7,3.1,4.4,1.4]),
                LabeledPoint(0.0, [4.8,3.4,1.6,0.2]),
                LabeledPoint(2.0, [4.4,3.2,1.3,0.2])]     

 model = LogisticRegressionWithSGD.train(sc.parallelize(parsed_data)) # gives error:
 # org.apache.spark.SparkException: Input validation failed.

 model = LogisticRegressionWithLBFGS.train(sc.parallelize(parsed_data), numClasses=3)  # works OK