@@ -503,56 +503,56 @@ <h3>1. np数组的构造<a class="headerlink" href="#np" title="Permalink to thi
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< p > 【c】随机矩阵: < code class ="docutils literal notranslate "> < span class ="pre "> np.random</ span > </ code > </ p >
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< p > 最常用的随机生成函数为 < code class ="docutils literal notranslate "> < span class ="pre "> rand,</ span > < span class ="pre "> randn,</ span > < span class ="pre "> randint,</ span > < span class ="pre "> choice</ span > </ code > ,它们分别表示0-1均匀分布的随机数组、标准正态的随机数组、随机整数组和随机列表抽样:</ p >
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< div class ="highlight-ipython notranslate "> < div class ="highlight "> < pre > < span > </ span > < span class ="gp "> In [38]: </ span > < span class ="n "> np</ span > < span class ="o "> .</ span > < span class ="n "> random</ span > < span class ="o "> .</ span > < span class ="n "> rand</ span > < span class ="p "> (</ span > < span class ="mi "> 3</ span > < span class ="p "> )</ span > < span class ="c1 "> # 生成服从0-1均匀分布的三个随机数</ span >
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- < span class ="gh "> Out[38]: </ span > < span class ="go "> array([0.70286261 , 0.16963837 , 0.56005106 ])</ span >
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+ < span class ="gh "> Out[38]: </ span > < span class ="go "> array([0.03413424 , 0.48828857 , 0.93909505 ])</ span >
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< span class ="gp "> In [39]: </ span > < span class ="n "> np</ span > < span class ="o "> .</ span > < span class ="n "> random</ span > < span class ="o "> .</ span > < span class ="n "> rand</ span > < span class ="p "> (</ span > < span class ="mi "> 3</ span > < span class ="p "> ,</ span > < span class ="mi "> 3</ span > < span class ="p "> )</ span > < span class ="c1 "> # 注意这里传入的不是元组,每个维度大小分开输入</ span >
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< span class ="gh "> Out[39]: </ span > < span class ="go "> </ span >
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- < span class ="go "> array([[0.10643401 , 0.97403626 , 0.63344678 ],</ span >
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- < span class ="go "> [0.66536365 , 0.23873862 , 0.38589388 ],</ span >
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- < span class ="go "> [0.32450925 , 0.84379175 , 0.50644027 ]])</ span >
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+ < span class ="go "> array([[0.40180614 , 0.52070528 , 0.07516936 ],</ span >
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+ < span class ="go "> [0.3129269 , 0.56649503 , 0.90187759 ],</ span >
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+ < span class ="go "> [0.25985401 , 0.84108489 , 0.58437083 ]])</ span >
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</ pre > </ div >
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</ div >
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< p > 对于服从区间 < span class ="math notranslate nohighlight "> \(a\)</ span > 到 < span class ="math notranslate nohighlight "> \(b\)</ span > 上的均匀分布可以如下生成:</ p >
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< div class ="highlight-ipython notranslate "> < div class ="highlight "> < pre > < span > </ span > < span class ="gp "> In [40]: </ span > < span class ="n "> a</ span > < span class ="p "> ,</ span > < span class ="n "> b</ span > < span class ="o "> =</ span > < span class ="mi "> 5</ span > < span class ="p "> ,</ span > < span class ="mi "> 15</ span >
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< span class ="gp "> In [41]: </ span > < span class ="p "> (</ span > < span class ="n "> b</ span > < span class ="o "> -</ span > < span class ="n "> a</ span > < span class ="p "> )</ span > < span class ="o "> *</ span > < span class ="n "> np</ span > < span class ="o "> .</ span > < span class ="n "> random</ span > < span class ="o "> .</ span > < span class ="n "> rand</ span > < span class ="p "> (</ span > < span class ="mi "> 3</ span > < span class ="p "> )</ span > < span class ="o "> +</ span > < span class ="n "> a</ span >
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- < span class ="gh "> Out[41]: </ span > < span class ="go "> array([7.58056042, 5.19864132, 6.34440414 ])</ span >
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+ < span class ="gh "> Out[41]: </ span > < span class ="go "> array([ 7.27987558, 12.30878755, 7.69601702 ])</ span >
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</ pre > </ div >
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</ div >
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< p > 一般的,可以选择已有的库函数:</ p >
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< div class ="highlight-ipython notranslate "> < div class ="highlight "> < pre > < span > </ span > < span class ="gp "> In [42]: </ span > < span class ="n "> np</ span > < span class ="o "> .</ span > < span class ="n "> random</ span > < span class ="o "> .</ span > < span class ="n "> uniform</ span > < span class ="p "> (</ span > < span class ="mi "> 5</ span > < span class ="p "> ,</ span > < span class ="mi "> 15</ span > < span class ="p "> ,</ span > < span class ="mi "> 3</ span > < span class ="p "> )</ span >
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- < span class ="gh "> Out[42]: </ span > < span class ="go "> array([14.38239745 , 9.85351137, 14.81961037 ])</ span >
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+ < span class ="gh "> Out[42]: </ span > < span class ="go "> array([10.18168665 , 5.15586065, 5.64472322 ])</ span >
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</ pre > </ div >
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</ div >
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< p > < code class ="docutils literal notranslate "> < span class ="pre "> randn</ span > </ code > 生成了 < span class ="math notranslate nohighlight "> \(N\rm{(\mathbf{0}, \mathbf{I})}\)</ span > 的标准正态分布:</ p >
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< div class ="highlight-ipython notranslate "> < div class ="highlight "> < pre > < span > </ span > < span class ="gp "> In [43]: </ span > < span class ="n "> np</ span > < span class ="o "> .</ span > < span class ="n "> random</ span > < span class ="o "> .</ span > < span class ="n "> randn</ span > < span class ="p "> (</ span > < span class ="mi "> 3</ span > < span class ="p "> )</ span >
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- < span class ="gh "> Out[43]: </ span > < span class ="go "> array([ 1.14531973, -0.09760709, 0.75457507 ])</ span >
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+ < span class ="gh "> Out[43]: </ span > < span class ="go "> array([-0.2310242 , 0.50286518, -0.61837552 ])</ span >
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< span class ="gp "> In [44]: </ span > < span class ="n "> np</ span > < span class ="o "> .</ span > < span class ="n "> random</ span > < span class ="o "> .</ span > < span class ="n "> randn</ span > < span class ="p "> (</ span > < span class ="mi "> 2</ span > < span class ="p "> ,</ span > < span class ="mi "> 2</ span > < span class ="p "> )</ span >
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< span class ="gh "> Out[44]: </ span > < span class ="go "> </ span >
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- < span class ="go "> array([[-2.5879568 , -0.08810583 ],</ span >
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- < span class ="go "> [-1.52652138, 0.74351561 ]])</ span >
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+ < span class ="go "> array([[ 0.31280442 , -0.34704761 ],</ span >
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+ < span class ="go "> [ 0.22871911, -1.50652482 ]])</ span >
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</ pre > </ div >
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</ div >
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< p > 对于服从方差为 < span class ="math notranslate nohighlight "> \(\sigma^2\)</ span > 均值为 < span class ="math notranslate nohighlight "> \(\mu\)</ span > 的一元正态分布可以如下生成:</ p >
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< div class ="highlight-ipython notranslate "> < div class ="highlight "> < pre > < span > </ span > < span class ="gp "> In [45]: </ span > < span class ="n "> sigma</ span > < span class ="p "> ,</ span > < span class ="n "> mu</ span > < span class ="o "> =</ span > < span class ="mf "> 2.5</ span > < span class ="p "> ,</ span > < span class ="mi "> 3</ span >
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< span class ="gp "> In [46]: </ span > < span class ="n "> mu</ span > < span class ="o "> +</ span > < span class ="n "> np</ span > < span class ="o "> .</ span > < span class ="n "> random</ span > < span class ="o "> .</ span > < span class ="n "> randn</ span > < span class ="p "> (</ span > < span class ="mi "> 3</ span > < span class ="p "> )</ span > < span class ="o "> *</ span > < span class ="n "> sigma</ span >
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- < span class ="gh "> Out[46]: </ span > < span class ="go "> array([-0.34486892, 7.77967389 , 2.7578818 ])</ span >
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+ < span class ="gh "> Out[46]: </ span > < span class ="go "> array([ 3.10129476, -1.66257161 , 3.7335879 ])</ span >
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</ pre > </ div >
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</ div >
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< p > 同样的,也可选择从已有函数生成:</ p >
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< div class ="highlight-ipython notranslate "> < div class ="highlight "> < pre > < span > </ span > < span class ="gp "> In [47]: </ span > < span class ="n "> np</ span > < span class ="o "> .</ span > < span class ="n "> random</ span > < span class ="o "> .</ span > < span class ="n "> normal</ span > < span class ="p "> (</ span > < span class ="mi "> 3</ span > < span class ="p "> ,</ span > < span class ="mf "> 2.5</ span > < span class ="p "> ,</ span > < span class ="mi "> 3</ span > < span class ="p "> )</ span >
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- < span class ="gh "> Out[47]: </ span > < span class ="go "> array([5.89785395, 4.75559493 , 3.90674484 ])</ span >
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+ < span class ="gh "> Out[47]: </ span > < span class ="go "> array([2.18487392, 6.74826945 , 3.76160619 ])</ span >
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</ pre > </ div >
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</ div >
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< p > < code class ="docutils literal notranslate "> < span class ="pre "> randint</ span > </ code > 可以指定生成随机整数的最小值最大值(不包含)和维度大小:</ p >
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< div class ="highlight-ipython notranslate "> < div class ="highlight "> < pre > < span > </ span > < span class ="gp "> In [48]: </ span > < span class ="n "> low</ span > < span class ="p "> ,</ span > < span class ="n "> high</ span > < span class ="p "> ,</ span > < span class ="n "> size</ span > < span class ="o "> =</ span > < span class ="mi "> 5</ span > < span class ="p "> ,</ span > < span class ="mi "> 15</ span > < span class ="p "> ,</ span > < span class ="p "> (</ span > < span class ="mi "> 2</ span > < span class ="p "> ,</ span > < span class ="mi "> 2</ span > < span class ="p "> )</ span > < span class ="c1 "> # 生成5到14的随机整数</ span >
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< span class ="gp "> In [49]: </ span > < span class ="n "> np</ span > < span class ="o "> .</ span > < span class ="n "> random</ span > < span class ="o "> .</ span > < span class ="n "> randint</ span > < span class ="p "> (</ span > < span class ="n "> low</ span > < span class ="p "> ,</ span > < span class ="n "> high</ span > < span class ="p "> ,</ span > < span class ="n "> size</ span > < span class ="p "> )</ span >
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< span class ="gh "> Out[49]: </ span > < span class ="go "> </ span >
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- < span class ="go "> array([[ 8, 11 ],</ span >
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- < span class ="go "> [ 8, 11 ]])</ span >
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+ < span class ="go "> array([[14, 8 ],</ span >
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+ < span class ="go "> [ 6, 9 ]])</ span >
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</ pre > </ div >
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</ div >
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< p > < code class ="docutils literal notranslate "> < span class ="pre "> choice</ span > </ code > 可以从给定的列表中,以一定概率和方式抽取结果,当不指定概率时为均匀采样,默认抽取方式为有放回抽样:</ p >
@@ -563,14 +563,14 @@ <h3>1. np数组的构造<a class="headerlink" href="#np" title="Permalink to thi
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< span class ="gp "> In [52]: </ span > < span class ="n "> np</ span > < span class ="o "> .</ span > < span class ="n "> random</ span > < span class ="o "> .</ span > < span class ="n "> choice</ span > < span class ="p "> (</ span > < span class ="n "> my_list</ span > < span class ="p "> ,</ span > < span class ="p "> (</ span > < span class ="mi "> 3</ span > < span class ="p "> ,</ span > < span class ="mi "> 3</ span > < span class ="p "> ))</ span >
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< span class ="gh "> Out[52]: </ span > < span class ="go "> </ span >
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- < span class ="go "> array([['d ', 'a ', 'c '],</ span >
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- < span class ="go "> ['a', 'c ', 'c '],</ span >
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- < span class ="go "> ['b ', 'd ', 'c ']], dtype='<U1')</ span >
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+ < span class ="go "> array([['c ', 'b ', 'd '],</ span >
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+ < span class ="go "> ['a', 'b ', 'a '],</ span >
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+ < span class ="go "> ['d ', 'a ', 'a ']], dtype='<U1')</ span >
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</ pre > </ div >
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</ div >
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< p > 当返回的元素个数与原列表相同时,不放回抽样等价于使用 < code class ="docutils literal notranslate "> < span class ="pre "> permutation</ span > </ code > 函数,即打散原列表:</ p >
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< div class ="highlight-ipython notranslate "> < div class ="highlight "> < pre > < span > </ span > < span class ="gp "> In [53]: </ span > < span class ="n "> np</ span > < span class ="o "> .</ span > < span class ="n "> random</ span > < span class ="o "> .</ span > < span class ="n "> permutation</ span > < span class ="p "> (</ span > < span class ="n "> my_list</ span > < span class ="p "> )</ span >
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- < span class ="gh "> Out[53]: </ span > < span class ="go "> array(['d ', 'c', 'a ', 'b '], dtype='<U1')</ span >
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+ < span class ="gh "> Out[53]: </ span > < span class ="go "> array(['a ', 'c', 'b ', 'd '], dtype='<U1')</ span >
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</ pre > </ div >
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</ div >
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< p > 最后,需要提到的是随机种子,它能够固定随机数的输出结果:</ p >
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