从0开始学习pyspark（八）：使用pyspark.ml.classification模块对蘑菇进行分类

数据下载：

数据为kaggle上的关于蘑菇分类的数据，地址：https://www.kaggle.com/uciml/mushroom-classification
也可在这里下载：https://github.com/ffzs/dataset/blob/master/mushrooms.csv

数据准备：

本数据集用于分类毒蘑菇和可食用蘑菇，共22个特征值，其中特征描述都是字符，用于机器学习的话，要将特征转换成数值。
在这里插入图片描述

from pyspark.sql import SparkSession
from pyspark import SparkConf, SparkContext
spark = SparkSession.builder.master('local[1]').appName('learn_ml').getOrCreate()

# 载入数据
df0 = spark.read.csv('file:///home/ffzs/python-projects/learn_spark/mushrooms.csv', header=True, inferSchema=True, encoding='utf-8')
# 查看是否有缺失值
# df0.toPandas().isna().sum()
df0.toPandas().isna().values.any()
# False 没有缺失值

# 先使用StringIndexer将字符转化为数值，然后将特征整合到一起
from pyspark.ml.feature import StringIndexer, VectorAssembler
old_columns_names = df0.columns
new_columns_names = [name+'-new' for name in old_columns_names]
for i in range(len(old_columns_names)):
    indexer = StringIndexer(inputCol=old_columns_names[i], outputCol=new_columns_names[i])
    df0 = indexer.fit(df0).transform(df0)
vecAss = VectorAssembler(inputCols=new_columns_names[1:], outputCol='features')
df0 = vecAss.transform(df0)
# 更换label列名
df0 = df0.withColumnRenamed(new_columns_names[0], 'label')

# 创建新的只有label和features的表
dfi = df0.select(['label', 'features'])

# 数据概观
dfi.show(5, truncate=0)

+-----+------------------------------------------------------------------------------+
|label|features                                                                      |
+-----+------------------------------------------------------------------------------+
|1.0  |(22,[1,3,4,7,8,9,10,19,20,21],[1.0,1.0,6.0,1.0,7.0,1.0,2.0,2.0,2.0,4.0])      |
|0.0  |(22,[1,2,3,4,8,9,10,19,20,21],[1.0,3.0,1.0,4.0,7.0,1.0,3.0,1.0,3.0,1.0])      |
|0.0  |(22,[0,1,2,3,4,8,9,10,19,20,21],[3.0,1.0,4.0,1.0,5.0,3.0,1.0,3.0,1.0,3.0,5.0])|
|1.0  |(22,[2,3,4,7,8,9,10,19,20,21],[4.0,1.0,6.0,1.0,3.0,1.0,2.0,2.0,2.0,4.0])      |
|0.0  |(22,[1,2,6,8,10,18,19,20,21],[1.0,1.0,1.0,7.0,2.0,1.0,1.0,4.0,1.0])           |
+-----+------------------------------------------------------------------------------+
only showing top 5 rows

# 将数据集分为训练集和测试集
train_data, test_data = dfi.randomSplit([4.0, 1.0], 100)

使用分类器进行分类：

逻辑回归,支持多项逻辑（softmax）和二项逻辑回归

pyspark.ml.classification.LogisticRegression(self, featuresCol="features", labelCol="label", predictionCol="prediction", maxIter=100, regParam=0.0, elasticNetParam=0.0, tol=1e-6, fitIntercept=True, threshold=0.5, thresholds=None, probabilityCol="probability", rawPredictionCol="rawPrediction", standardization=True, weightCol=None, aggregationDepth=2, family="auto")

部分参数

regParam: 正则化参数(>=0)
elasticNetParam: ElasticNet混合参数，0-1之间，当alpha为0时,惩罚为L2正则化，当为1时为L1正则化
fitIntercept: 是否拟合一个截距项
Standardization：是否在拟合数据之前对数据进行标准化
aggregationDepth: 树聚合所建议的深度(>=2)

from pyspark.ml.classification import LogisticRegression
blor = LogisticRegression(regParam=0.01)
blorModel = blor.fit(train_data)
result = blorModel.transform(test_data)

# 计算准确率
result.filter(result.label == result.prediction).count()/result.count()
# 0.9661954517516902

决策树（Decision tree）

pyspark.ml.classification.DecisionTreeClassifier(featuresCol='features', labelCol='label', predictionCol='prediction', probabilityCol='probability', rawPredictionCol='rawPrediction', maxDepth=5, maxBins=32, minInstancesPerNode=1, minInfoGain=0.0, maxMemoryInMB=256, cacheNodeIds=False, checkpointInterval=10, impurity='gini', seed=None)

部分参数

checkpointInterval：设置checkpoint区间(>=1)，或宕掉checkpoint(-1)，例如10意味着缓冲区(cache)将会每迭代10次获得一次checkpoint
fit(datasset,params=None)
impurity: 信息增益计算的准则，选项"entropy", “gini”
maxBins：连续特征离散化的最大分箱，必须>=2 并且>=分类特征分类的数量
maxDepth：树的最大深度
minInfoGain：分割结点所需的最小的信息增益
minInstancesPerNode：每个结点最小实例个数

from pyspark.ml.classification import DecisionTreeClassifier
dt = DecisionTreeClassifier(maxDepth=5)
dtModel = dt.fit(train_data)
result = dtModel.transform(test_data)

# accuracy
result.filter(result.label == result.prediction).count()/result.count()
# 1.0

梯度增强树（Gradient boosting tree）

pyspark.ml.classification.GBTClassifier(featuresCol='features', labelCol='label', predictionCol='prediction', maxDepth=5, maxBins=32, minInstancesPerNode=1, minInfoGain=0.0, maxMemoryInMB=256, cacheNodeIds=False, checkpointInterval=10, lossType='logistic', maxIter=20, stepSize=0.1, seed=None, subsamplingRate=1.0)

部分参数

checkpointInterval: 同DecisionTreeClassifier
fit(dataset,params=None)方法
lossType: GBT要最小化的损失函数，选项：logistic
maxBins: 同DecisionTreeClassifier
maxDepth: 同DecisionTreeClassifier
maxIter: 同DecisionTreeClassifier
minInfoGain: 同DecisionTreeClassifier
minInstancesPerNode：同DecisionTreeClassifier
stepSize: 每次迭代优化的步长
subsamplingRate: 同RandomForesetClassier

from pyspark.ml.classification import GBTClassifier
gbt = GBTClassifier(maxDepth=5)
gbtModel = gbt.fit(train_data)
result = gbtModel.transform(test_data)

# accuracy
result.filter(result.label == result.prediction).count()/result.count()
# 1.0

随机森林（Random forest）

pyspark.ml.classification.RandomForestClassifier(featuresCol='features', labelCol='label', predictionCol='prediction', probabilityCol='probability', rawPredictionCol='rawPrediction', maxDepth=5, maxBins=32, minInstancesPerNode=1, minInfoGain=0.0, maxMemoryInMB=256, cacheNodeIds=False, checkpointInterval=10, impurity='gini', numTrees=20, featureSubsetStrategy='auto', seed=None, subsamplingRate=1.0)

部分参数

checkpoint：同DecisionTreeClassifier
featureSubsetStrategy：每棵树上要分割的特征数目，选项为"auto",“all”, “onethird”, “sqrt”, “log2”, “(0.0-1.0],”[1-n]"
fit(dataset,params=None)方法
impurity: 同DecisionTreeClassifier
maxBins:同DecisionTreeClassifier
maxDepth：同DecisionTreeClassifier
minInfoGain: 同DecisionTreeClassifier
numTrees: 训练树的个数
subsamplingRate: 用于训练每颗决策树的样本个数，区间(0,1]

from pyspark.ml.classification import RandomForestClassifier
rf = RandomForestClassifier(numTrees=10, maxDepth=5)
rfModel = rf.fit(train_data)
result = rfModel.transform(test_data)

# accuracy
result.filter(result.label == result.prediction).count()/result.count()
# 1.0

朴素贝叶斯（Naive bayes）

pyspark.ml.classification.NaiveBayes(featuresCol='features', labelCol='label', predictionCol='prediction', probabilityCol='probability', rawPredictionCol='rawPrediction', smoothing=1.0, modelType='multinomial', thresholds=None, weightCol=None)

部分参数

modelType: 选项：multinomial（多项式）和bernoulli（伯努利）
smoothing: 平滑参数，应该>=0，默认为1.0

from pyspark.ml.classification import NaiveBayes
nb = NaiveBayes()
nbModel = nb.fit(train_data)
result = nbModel.transform(test_data)

#accuracy
result.filter(result.label == result.prediction).count()/result.count()
#0.9231714812538414

支持向量机（SVM）

pyspark.ml.classification.LinearSVC(featuresCol='features', labelCol='label', predictionCol='prediction', maxIter=100, regParam=0.0, tol=1e-06, rawPredictionCol='rawPrediction', fitIntercept=True, standardization=True, threshold=0.0, weightCol=None, aggregationDepth=2)

from pyspark.ml.classification import LinearSVC
svm = LinearSVC(maxIter=10, regPcaram=0.01)
svmModel = svm.fit(train_data)
result = svmModel.transform(test_data)

# accuracy
result.filter(result.label == result.prediction).count()/result.count()
# 0.9797172710510141