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  • numpy的聚合运算及其索引和排序

    一:常用的聚合运算有

    (1)求和sum

    (2)最大值max

    (3)最小值min

    (4)平均值average

    (5)中位数median

    (6)prod,对所有的元素进行乘积

    (7)percentile:百分比

    (8)var:方差

    (9)std:标准差

    二:代码举例说明

    import numpy as np
    
    L = np.random.random(1000000)
    print("L = ",L)
    
    print("sum = ",np.sum(L))
    
    print("max = ",np.max(L))
    
    print("min = ",np.min(L))
    
    print("average = ",np.average(L))
    
    print("median = ",np.median(L))
    
    print("prod = ",np.prod(L))
    
    print("percentile = ",np.percentile(L,50))
    
    print("var = ",np.var(L))
    
    print("std = ",np.std(L))
    
    
    '''
    L =  [0.83190736 0.74081446 0.48812662 ... 0.27353513 0.90351821 0.99799109]
    sum =  499602.0936992654
    max =  0.9999994792249605
    min =  1.1307318972253455e-06
    average =  0.4996020936992654
    median =  0.49924280325258924
    prod =  0.0
    percentile =  0.49924280325258924
    var =  0.0832567557942998
    std =  0.2885424679216212
    '''

     三:索引

    import numpy as np
    
    x = np.random.normal(0,1,size=1000000)
    print(x)
    
    print(np.min(x))
    index_min = np.argmin(x)
    print(x[index_min])
    
    print(np.max(x))
    index_max = np.argmax(x)
    print(x[index_max])

    四:排序及其索引

    import numpy as np
    
    
    arr = np.arange(10)
    np.random.shuffle(arr)
    print(arr)
    print(np.sort(arr)) #从小到大排序,但是不改变原先的向量
    print(np.argsort(arr))#打印的是从小到大的元素所在的下标

     五:partition

    import numpy as np
    
    
    arr = np.arange(10)
    np.random.shuffle(arr)
    print(arr)#[8 1 5 9 6 3 7 4 0 2]
    
    print(np.partition(arr,4))#[1 3 2 0 4 5 6 7 9 8]

    类似于快速排序,4就是我们所选的基数,4之前的都比4小,4之后的都比4大。

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  • 原文地址:https://www.cnblogs.com/lyr999736/p/10627836.html
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