Python---计算mAP

  对于怎么计算precision和recall可以参考对于http://blog.csdn.net/freeape/article/details/52090515

1 通过precision和recall计算ap

#!/usr/bin/python
# -*- coding: UTF-8 -*-
# author: yicm****@gmail.com

import argparse
import sys
from numpy import *
import numpy as np

#prec =  0.942857
#rec =   0.71895
#ap = 0.67786704015

def parse_args():
    """Parse input arguments."""
    parser = argparse.ArgumentParser(description='AP Calculation')

    parser.add_argument('--prec', dest='precision', help='The Precision Value',
            default=0.0, type=float)
    parser.add_argument('--rec', dest='recall', help='The Recall Value',
            default=0.0, type=float)

    args = parser.parse_args()

    return args

def calc_ap(prec, rec):
    mrec = np.array([0, rec, 1])
    mpre = np.array([0, prec, 0])

    for i in range(mrec.size - 2, -1, -1):
        mpre[i] = max(mpre[i], mpre[i+1]);
        #print mpre[i]

    #print mrec[1 : ]
    #print mrec[0 : 2]

    idx1 = np.where(mrec[1 : ]   != mrec[0 : 2])
    idx2 = [x + 1 for x in idx1]

    #print mrec.take(idx2)
    #print mrec.take(idx1)

    ap = sum((mrec.take(idx2) - mrec.take(idx1)) * mpre.take(idx2))
    print "ap = " + str(ap)
    return ap

if __name__ == "__main__":
    args = parse_args()

    #len(sys.argv)
    print "args.precision: {}".format(args.precision)
    print "args.recall: {}".format(args.recall)
    calc_ap(args.precision, args.recall)

2 通过ap计算mAP

Mean Average Precision(mAP)，平均精度计算。

mAP = sum(ap)/N

3 附matlab ap计算代码

另附Matlab代码：

prec =  0.371429
rec =   0.97744
mrec=[0 ; rec ; 1];
mpre=[0 ; prec ; 0];
for i=numel(mpre)-1:-1:1
    mpre(i)=max(mpre(i),mpre(i+1));
end

i=find(mrec(2:end)~=mrec(1:end-1))+1;
ap=sum((mrec(i)-mrec(i-1)) .* mpre(i))