@@ -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([0.19644779 , 0.05829755 , 0.1763729 ])</ span >
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+ < span class ="gh "> Out[38]: </ span > < span class ="go "> array([0.31716937 , 0.0257562 , 0.1757882 ])</ 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([[0.81234435 , 0.3204975 , 0.46507329 ],</ span >
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- < span class ="go "> [0.15952536 , 0.56821002 , 0.90365527 ],</ span >
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- < span class ="go "> [0.73249233 , 0.00373533 , 0.70851416 ]])</ span >
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+ < span class ="go "> array([[0.09218596 , 0.02981407 , 0.78171316 ],</ span >
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+ < span class ="go "> [0.01116467 , 0.79777235 , 0.26795529 ],</ span >
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+ < span class ="go "> [0.47509305 , 0.98702896 , 0.63964399 ]])</ 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([6.68214573, 5.10422845, 9.83236843 ])</ span >
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+ < span class ="gh "> Out[41]: </ span > < span class ="go "> array([ 5.84238915, 13.9787058 , 5.43238762 ])</ 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([7.54869551, 9.99776418, 6.17509434 ])</ span >
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+ < span class ="gh "> Out[42]: </ span > < span class ="go "> array([10.93549541, 14.21013578, 6.46852749 ])</ 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([ 0.19822997 , -0.42655702 , 0.54141998 ])</ span >
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+ < span class ="gh "> Out[43]: </ span > < span class ="go "> array([ 0.54801691 , -0.46540686 , 0.65733351 ])</ 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([[-1.05118329, 1.16228097 ],</ span >
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- < span class ="go "> [-1.20598525, -0.43466828 ]])</ span >
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+ < span class ="go "> array([[-2.10673238, -0.85087355 ],</ span >
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+ < span class ="go "> [-0.45202665, 0.56211032 ]])</ 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([7.03818638, 2.43763313, 3.28032122 ])</ span >
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+ < span class ="gh "> Out[46]: </ span > < span class ="go "> array([ 2.7220844 , -0.71042638, 3.10171717 ])</ 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([3.07728292, 3.20987623 , 4.61403821 ])</ span >
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+ < span class ="gh "> Out[47]: </ span > < span class ="go "> array([1.99030477, 6.59505467 , 4.62269539 ])</ 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([[11, 7 ],</ span >
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- < span class ="go "> [ 5, 5 ]])</ span >
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+ < span class ="go "> array([[14, 11 ],</ span >
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+ < span class ="go "> [ 5, 12 ]])</ 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([['c', 'c ', 'd '],</ span >
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- < span class ="go "> ['a ', 'a ', 'd'],</ span >
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- < span class ="go "> ['a', 'c ', 'b ']], dtype='<U1')</ span >
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+ < span class ="go "> array([['c', 'b ', 'c '],</ span >
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+ < span class ="go "> ['b ', 'd ', 'd'],</ span >
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+ < span class ="go "> ['a', 'a ', 'd ']], 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(['b ', 'a ', 'c ', 'd '], dtype='<U1')</ span >
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+ < span class ="gh "> Out[53]: </ span > < span class ="go "> array(['d ', 'c ', 'b ', 'a '], 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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