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31 lines
1.3 KiB
Python
31 lines
1.3 KiB
Python
import numpy as np
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def conf_matrix(p,labels,names=['1','0'],threshold=.5,show=True):
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"""
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Returns error rate and true/false positives in a binary classification problem
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- Actual classes are displayed by column.
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- Predicted classes are displayed by row.
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:param p: array of class '1' probabilities.
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:param labels: array of actual classes.
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:param names: list of class names, defaults to ['1','0'].
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:param threshold: probability value used to decide the class.
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:param show: whether the matrix should be shown or not
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:type show: False|True
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"""
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assert p.size == labels.size, "Arrays p and labels have different dimensions."
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decision = np.ones((labels.size,1))
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decision[p<threshold] = 0
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diff = decision - labels
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false_0 = diff[diff == -1].size
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false_1 = diff[diff == 1].size
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true_1 = np.sum(decision[diff ==0])
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true_0 = labels.size - true_1 - false_0 - false_1
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error = (false_1 + false_0)/np.float(labels.size)
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if show:
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print 100. - error * 100,'% instances correctly classified'
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print '%-10s| %-10s| %-10s| ' % ('',names[0],names[1])
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print '----------|------------|------------|'
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print '%-10s| %-10s| %-10s| ' % (names[0],true_1,false_0)
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print '%-10s| %-10s| %-10s| ' % (names[1],false_1,true_0)
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return error,true_1, false_1, true_0, false_0
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