Numpy Learning Notes-np.argsort()

最新推荐文章于 2024-01-25 16:25:02 发布

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最新推荐文章于 2024-01-25 16:25:02 发布

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分类专栏： Numpy

本文链接：https://blog.youkuaiyun.com/qq_23557345/article/details/88080445

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本文介绍在SSD目标检测算法中如何利用numpy的argsort()函数找到最大的概率类别及其对应的边界框。通过一个示例详细解释了argsort()函数的工作原理，即返回数组元素从小到大的索引值。

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In the ssd objects detection algorithm,I need to find out the top 400(according to the paper) bouding boxes in the total 87732 anchor boxes.Therefore,we need a method to find out the maximum propabilities classes and it's corresponding boxes,and we call the propabilities as scores. np.argsort() may be a good function for that goal,it will return the sorted index from the smallest to the largest.Function and it's arguments list as follows:

np.argsort(a,axis=-1,kind='quicksort',order=None)

a- a 1D array

axis- the dimention of sort.

The most important points about this function are:1.function will return the index of sorted array rather than arguments in the array.2.The sort order is from smallest to the largest.

There is an example to explain this function:

import numpy as np
a=np.array([1,4,2,4,6,6,2,8])
b=np.argsort(a,axis=-1)
print(b)

Results:[0,2,6,1,3,4,5,7]

As we can see in the front examples,the minimum arguments in array a is 1 and it's index is 0,and the second smallest arguments is 2 in the index of 2 ... and so on.