SVM算法实例

机器学习算法完整版见fenghaootong-github
<https://github.com/fenghaotong/MachineLearning/tree/master/SVM>

MINST for SVM

导入模块
from sklearn import svm import pandas as pd import time
导入数据
df = pd.read_csv('../DATA/train.csv') labels = df.as_matrix(columns=['label'])
#find lable to transform to matrix dataset = df.drop('label', axis=1
).as_matrix()#transform dataset to matrxi without drop lable dataset = dataset
/ (28.0*28.0) int(len(labels.ravel()) * 0.75) 31500
数据分为训练和验证集
train_len = int(len(labels.ravel()) * 0.75) train_dataset =
dataset[:train_len] train_labels = labels[:train_len] valid_dataset =
dataset[train_len:] valid_labels = labels[train_len:] train_labels.ravel()
array([1, 0, 1, ..., 2, 9, 5])
模型训练
t0 = time.time() clf = svm.SVC(C=10000.0,kernel='rbf') clf.fit(train_dataset,
train_labels.ravel()) print("train-time:",round(time.time() - t0, 3), "s")
train-time: 115.624 s
模型预测
predictions = [int(a) for a in clf.predict(valid_dataset)] #predictions sum = 0
for a, y in zip(predictions, valid_labels.ravel()): if a == y: sum = sum + 1
print ("%s of %s test values correct.\ntest accuracy: %f" % (sum,
len(valid_labels.ravel()), sum / len(valid_labels.ravel()))) 950 of 1050 test
values correct. test accuracy: 0.904762
换参比较
def svm_baseline(kernel): sum = 0 t0 = time.time() clf = svm.SVC(C=10000.0
,kernel=kernel) clf.fit(train_dataset, train_labels.ravel()) print("train-time:"
,round(time.time() - t0,3), "s") predictions = [int(a) for a in
clf.predict(valid_dataset)]for a, y in zip(predictions, valid_labels.ravel()):
if a == y: sum = sum + 1 print ("%s of %s test values correct.\ntest accuracy:
%f" % (sum, len(valid_labels.ravel()), sum / len(valid_labels.ravel())))
kernels = ['rbf','linear'] for kernel in kernels: svm_baseline(kernel)
train-time: 2.6730403900146484 s 951 of 1050 test values correct. test
accuracy: 0.905714 train-time: 2.0404305458068848 s 950 of 1050 test values
correct. test accuracy: 0.904762
SVM参数 <https://zhuanlan.zhihu.com/p/31264935>

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