概述
scikit-learn 是机器学习领域非常热门的一个开源库,基于Python 语言写成。可以免费使用。 而且使用非常的简单,文档感人,非常值得去学习。
下面是一张scikit-learn的图谱:
我们可以看到,机器学习分为四大块,分别是 classification (分类), clustering (聚类), regression (回归), dimensionality reduction (降维)。
安装scikit-learn
如果使用的是ubuntu
则非常的简单,直接sudo apt-get install scikit-learn
即可,这里可能会有要你安装别的依赖,也是同样的安装方法,如果是别的linux
版本,可使用pip
等工具进行安装。
测试:
# 不报错则表示安装成功>>> import sklearn>>> 123
安装XGBDT
本质上还是GBDT,只是对GBDT进行了一些更改,叫X (Extreme) GBoosted,它把速度和效率做到了极致。在scikit-learn目前还没有这个分类器,因此要进行单独的安装。
这里对linux的安装进行说明,其余操作系统见:
http://xgboost.readthedocs.io/en/latest/build.html
# 拉取源码包git clone --recursive https://github.com/dmlc/xgboostcd xgboost# 编译make -j4# python包的安装# 首先安装工具sudo apt-get install python-setuptools# 进入目录,安装cd python-package
sudo python setup.py install# 测试不报错,成功>>> import xgboost
>>> 12345678910111213141516
scikit-learn测试
测试的数据为,美国一个区域的糖尿病的情况,具有以下的信息:
Attribute Information:
1. Number of times pregnant
2. Plasma glucose concentration a 2 hours in an oral glucose tolerance test
3. Diastolic blood pressure (mm Hg)
4. Triceps skin fold thickness (mm)
5. 2-Hour serum insulin (mu U/ml)
6. Body mass index (weight in kg/(height in m)^2)
7. Diabetes pedigree function
8. Age (years)
9. Class variable (0 or 1)
第9个是标签,即我们要预测的情况,0表示没有患病,1表示患病,数据集下载地址:
https://archive.ics.uci.edu/ml/datasets/Pima+Indians+Diabetes
完整代码如下,可以进行一键测试多个算法:
#!usr/bin/env python #-*- coding: utf-8 -*- import time
from sklearn import metrics
import numpy as np
from numpy import *from sklearn import cross_validation# Multinomial Naive Bayes Classifier def naive_bayes_classifier(train_x, train_y):
from sklearn.naive_bayes import MultinomialNB
model = MultinomialNB(alpha=0.01)
model.fit(train_x, train_y)
return model
# KNN Classifier def knn_classifier(train_x, train_y):
from sklearn.neighbors import KNeighborsClassifier
model = KNeighborsClassifier(n_neighbors=10)
model.fit(train_x, train_y)
return model
# Logistic Regression Classifier def logistic_regression_classifier(train_x, train_y):
from sklearn.linear_model import LogisticRegression
model = LogisticRegression(penalty='l2')
model.fit(train_x, train_y)
return model
# Random Forest Classifier def random_forest_classifier(train_x, train_y):
from sklearn.ensemble import RandomForestClassifier
model = RandomForestClassifier(n_estimators=100)
model.fit(train_x, train_y)
return model
# Decision Tree Classifier def decision_tree_classifier(train_x, train_y):
from sklearn import tree
model = tree.DecisionTreeClassifier()
model.fit(train_x, train_y)
return model
# GBDT(Gradient Boosting Decision Tree) Classifier def gradient_boosting_classifier(train_x, train_y):
from sklearn.ensemble import GradientBoostingClassifier
model = GradientBoostingClassifier(n_estimators=40)
model.fit(train_x, train_y)
return model
# SVM Classifier def svm_classifier(train_x, train_y):
from sklearn.svm import SVC
model = SVC(kernel='rbf', probability=True)
model.fit(train_x, train_y)
return model
# SVM Classifier using cross validation def svm_cross_validation(train_x, train_y):
from sklearn.grid_search import GridSearchCV
from sklearn.svm import SVC
model = SVC(kernel='rbf', probability=True)
param_grid = {'C': [1e-3, 1e-2, 1e-1, 1, 10, 100, 1000], 'gamma': [0.001, 0.0001]}
grid_search = GridSearchCV(model, param_grid, n_jobs = 1, verbose=1)
grid_search.fit(train_x, train_y)
best_parameters = grid_search.best_estimator_.get_params()
for para, val in best_parameters.items():
print para, val
model = SVC(kernel='rbf', C=best_parameters['C'], gamma=best_parameters['gamma'], probability=True)
model.fit(train_x, train_y)
return model
# XGBoost Classfierdef extreme_gradient_boosting_classifier(train_x,train_y):
import xgboost
model = xgboost.XGBClassifier()
model.fit(train_x,train_y) return model# read datasetdef read_data():
dataset = np.loadtxt('diabetes.txt',delimiter=',')
x = dataset[:,:8]
y = dataset[:,8]
seed = 7
test_size = 0.33
# split the dataset
train_x,test_x,train_y,test_y = cross_validation.train_test_split \
(x,y,test_size=test_size,random_state=seed) return train_x, test_x, train_y, test_y
if __name__ == '__main__':
test_classifiers = ['NB','RF','SVM','KNN','LR','DT','GBDT','XGBDT']
classifiers = {'NB':naive_bayes_classifier,
'KNN':knn_classifier,
'LR':logistic_regression_classifier,
'RF':random_forest_classifier,
'DT':decision_tree_classifier,
'SVM':svm_classifier,
'SVMCV':svm_cross_validation,
'GBDT':gradient_boosting_classifier,
'XGBDT':extreme_gradient_boosting_classifier
}
print 'reading training and testing data...'
train_x, test_x, train_y, test_y = read_data()
num_train, num_feat = train_x.shape
num_test, num_feat = test_x.shape
is_binary_class = (len(np.unique(train_y)) == 2)
print '******************** Data Info *********************'
print '#training data: %d, #testing_data: %d, dimension: %d' % (num_train, num_test, num_feat)
for classifier in test_classifiers:
print '******************* %s ********************' % classifier
start_time = time.time()
model = classifiers[classifier](train_x, train_y)
print 'training took %fs!' % (time.time() - start_time)
predict = model.predict(test_x)
if is_binary_class:
precision = metrics.precision_score(test_y, predict)
recall = metrics.recall_score(test_y, predict)
print 'precision: %.2f%%, recall: %.2f%%' % (100 * precision, 100 * recall)
accuracy = metrics.accuracy_score(test_y, predict)
print 'accuracy: %.2f%%' % (100 * accuracy) 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132
运行结果,可以看到在此问题上XGBDT效果稍微好一点,但是这是没有经过调参的,可以进行调参等预处理操作来改善效果。
yqtao@yqtao:~/machine-learn$ python sklean.py
reading training and testing data...******************** Data Info *********************#training data: 514, #testing_data: 254, dimension: 8******************* NB ********************training took 0.001360s!
precision: 48.35%, recall: 47.83%
accuracy: 62.60%******************* RF ********************training took 0.198425s!
precision: 71.26%, recall: 67.39%
accuracy: 78.35%******************* SVMCV ********************Fitting 3 folds for each of 14 candidates, totalling 42 fits
[Parallel(n_jobs=1)]: Done 42 out of 42 | elapsed: 1.5s finishedkernel rbfC 1verbose Falseprobability Truedegree 3shrinking Truemax_iter -1decision_function_shape Nonerandom_state Nonetol 0.001cache_size 200coef0 0.0gamma 0.0001class_weight Nonetraining took 1.536800s!precision: 69.84%, recall: 47.83%accuracy: 73.62%******************* KNN ********************training took 0.003870s!precision: 71.21%, recall: 51.09%accuracy: 74.80%******************* LR ********************training took 0.003629s!precision: 70.83%, recall: 55.43%accuracy: 75.59%******************* DT ********************training took 0.002498s!precision: 61.18%, recall: 56.52%accuracy: 71.26%******************* GBDT ********************training took 0.033451s!precision: 70.73%, recall: 63.04%accuracy: 77.17%******************* XGBDT ********************training took 0.232969s!precision: 70.45%, recall: 67.39%accuracy: 77.95%12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152
参考资料:
http://scikit-learn.org/stable/
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