如何用python画好confusion matrix

在做分类的时候，经常需要画混淆矩阵，下面我们使用python的matplotlib包，scikit-learning机器学习库也同样提供了例子：http://scikit-learn.org/stable/auto_examples/plot_confusion_matrix.html， 但是这样的图并不能满足我们的要求，

首先是刻度的显示是在方格的中间，这需要隐藏刻度，其次是如何把每个label显示在每个方块的中间， 其次是如何在每个方格中显示accuracy数值， 最后是如何在横坐标和纵坐标显示label的名字，在label name比较长的时候，如何处理显示问题。

直接贴上代码：下载见 https://github.com/guoyilin/plot.git

'''compute confusion matrix
labels.txt: contain label name.
predict.txt: predict_label true_label
'''
from sklearn.metrics import confusion_matrix
import matplotlib.pyplot as plt
import numpy as np
#load labels.
labels = []
file = open('labels.txt', 'r')
lines = file.readlines()
for line in lines:
	labels.append(line.strip())
file.close()

y_true = []
y_pred = []
#load true and predict labels.
file = open('predict.txt', 'r')
lines = file.readlines()
for line in lines:
	y_true.append(int(line.split(" ")[1].strip()))
	y_pred.append(int(line.split(" ")[0].strip()))
file.close()
tick_marks = np.array(range(len(labels))) + 0.5
def plot_confusion_matrix(cm, title='Confusion Matrix', cmap = plt.cm.binary):
    plt.imshow(cm, interpolation='nearest', cmap=cmap)
    plt.title(title)
    plt.colorbar()
    xlocations = np.array(range(len(labels)))
    plt.xticks(xlocations, labels, rotation=90)
    plt.yticks(xlocations, labels)
    plt.ylabel('True label')
    plt.xlabel('Predicted label')
cm = confusion_matrix(y_true, y_pred)
print cm
np.set_printoptions(precision=2)
cm_normalized = cm.astype('float')/cm.sum(axis=1)[:, np.newaxis]
print cm_normalized
plt.figure(figsize=(12,8), dpi=120)
#set the fontsize of label.
#for label in plt.gca().xaxis.get_ticklabels():
#    label.set_fontsize(8)
#text portion
ind_array = np.arange(len(labels))
x, y = np.meshgrid(ind_array, ind_array)

for x_val, y_val in zip(x.flatten(), y.flatten()):
    c = cm_normalized[y_val][x_val]
    if (c > 0.01):
	plt.text(x_val, y_val, "%0.2f" %(c,), color='red', fontsize=7, va='center', ha='center')
#offset the tick
plt.gca().set_xticks(tick_marks, minor=True)
plt.gca().set_yticks(tick_marks, minor=True)
plt.gca().xaxis.set_ticks_position('none')
plt.gca().yaxis.set_ticks_position('none')
plt.grid(True, which='minor', linestyle='-')
plt.gcf().subplots_adjust(bottom=0.15)

plot_confusion_matrix(cm_normalized, title='Normalized confusion matrix')
#show confusion matrix
plt.show()

结果如下图所示：