一般来说没有文档,因为作为星火1.6/2.0最相关的API并不打算是公共的,应在星火2.1.0(见SPARK-7146)更改。
API是比较复杂的,因为它必须遵循特定的惯例,以使给定Transformer
或Estimator
兼容与Pipeline
API。这些方法中的一些可能是读写和网格搜索等功能所必需的。其他,如keyword_only
只是一个简单的帮手,而不是严格要求。
假设您已经定义了以下的配料插件均值参数:
from pyspark.ml.pipeline import Estimator, Model, Pipeline
from pyspark.ml.param.shared import *
from pyspark.sql.functions import avg, stddev_samp
class HasMean(Params):
mean = Param(Params._dummy(), "mean", "mean",
typeConverter=TypeConverters.toFloat)
def __init__(self):
super(HasMean, self).__init__()
def setMean(self, value):
return self._set(mean=value)
def getMean(self):
return self.getOrDefault(self.mean)
标准偏差参数:
class HasStandardDeviation(Params):
stddev = Param(Params._dummy(), "stddev", "stddev",
typeConverter=TypeConverters.toFloat)
def __init__(self):
super(HasStandardDeviation, self).__init__()
def setStddev(self, value):
return self._set(stddev=value)
def getStddev(self):
return self.getOrDefault(self.stddev)
和门槛:
class HasCenteredThreshold(Params):
centered_threshold = Param(Params._dummy(),
"centered_threshold", "centered_threshold",
typeConverter=TypeConverters.toFloat)
def __init__(self):
super(HasCenteredThreshold, self).__init__()
def setCenteredThreshold(self, value):
return self._set(centered_threshold=value)
def getCenteredThreshold(self):
return self.getOrDefault(self.centered_threshold)
您可以创建基本Estimator
为如下:
class NormalDeviation(Estimator, HasInputCol,
HasPredictionCol, HasCenteredThreshold):
def _fit(self, dataset):
c = self.getInputCol()
mu, sigma = dataset.agg(avg(c), stddev_samp(c)).first()
return (NormalDeviationModel()
.setInputCol(c)
.setMean(mu)
.setStddev(sigma)
.setCenteredThreshold(self.getCenteredThreshold())
.setPredictionCol(self.getPredictionCol()))
class NormalDeviationModel(Model, HasInputCol, HasPredictionCol,
HasMean, HasStandardDeviation, HasCenteredThreshold):
def _transform(self, dataset):
x = self.getInputCol()
y = self.getPredictionCol()
threshold = self.getCenteredThreshold()
mu = self.getMean()
sigma = self.getStddev()
return dataset.withColumn(y, (dataset[x] - mu) > threshold * sigma)
最后,可以使用如下:
df = sc.parallelize([(1, 2.0), (2, 3.0), (3, 0.0), (4, 99.0)]).toDF(["id", "x"])
normal_deviation = NormalDeviation().setInputCol("x").setCenteredThreshold(1.0)
model = Pipeline(stages=[normal_deviation]).fit(df)
model.transform(df).show()
## +---+----+----------+
## | id| x|prediction|
## +---+----+----------+
## | 1| 2.0| false|
## | 2| 3.0| false|
## | 3| 0.0| false|
## | 4|99.0| true|
## +---+----+----------+
的感谢!所以Estimator的状态也被认为是一个参数? –
您是否将估算器的参数调整为模型参数?如果是这样,这种设计方式很方便,但对于基本实现来说并不难。 – zero323
好的,任何希望得到一些关于如何坚持像这样的自定义步骤的建议? –