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<h2 id="使用array创建矩阵"><a href="#使用array创建矩阵" class="headerlink" title="使用array创建矩阵"></a>使用array创建矩阵</h2><figure class="highlight lsl"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">import numpy as np</span><br><span class="line">#创建向量/矩阵</span><br><span class="line">a=np.array([<span class="number">5</span>,<span class="number">10</span>,<span class="number">15</span>,<span class="number">20</span>])</span><br><span class="line">b=np.array([[<span class="number">1</span>,<span class="number">2</span>,<span class="number">3</span>,<span class="number">4</span>],[<span class="number">5</span>,<span class="number">6</span>,<span class="number">7</span>,<span class="number">8</span>],[<span class="number">9</span>,<span class="number">10</span>,<span class="number">11</span>,<span class="number">12</span>]])</span><br><span class="line">#输出行列数</span><br><span class="line">a.shape</span><br><span class="line">b.shape</span><br><span class="line">b.shape[<span class="number">0</span>]</span><br><span class="line">#修改行列数</span><br><span class="line">b.shape=<span class="number">4</span>,<span class="number">3</span> </span><br><span class="line">c=b.reshape((<span class="number">2</span>,<span class="number">-1</span>)) #此处b和c共享内存</span><br><span class="line">#转置</span><br><span class="line">b.T</span><br><span class="line">#指定数据类型</span><br><span class="line">d=np.array([[<span class="number">1</span>,<span class="number">2</span>,<span class="number">3</span>,<span class="number">4</span>],[<span class="number">5</span>,<span class="number">6</span>,<span class="number">7</span>,<span class="number">8</span>],[<span class="number">9</span>,<span class="number">10</span>,<span class="number">11</span>,<span class="number">12</span>]],dtype=np.<span class="type">float</span>)</span><br><span class="line">#转换数据类型</span><br><span class="line">f=d.astype(np.int) #np.bool/np.complex</span><br></pre></td></tr></table></figure>
<h2 id="使用函数创建矩阵"><a href="#使用函数创建矩阵" class="headerlink" title="使用函数创建矩阵**"></a>使用<strong><strong>函数</strong></strong>创建矩阵**</h2><figure class="highlight routeros"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">#等差(指定公差)</span></span><br><span class="line"><span class="attribute">a</span>=np.arange(1,5,0.5)</span><br><span class="line"></span><br><span class="line"><span class="comment">#等差(指定个数)</span></span><br><span class="line"><span class="attribute">b</span>=np.linspace(1,10,10)</span><br><span class="line"><span class="attribute">b</span>=np.linspace(1,10,10, <span class="attribute">endpoint</span>=<span class="literal">False</span>) #endpoint指定是否包括终值</span><br><span class="line"></span><br><span class="line"><span class="comment">#等比</span></span><br><span class="line"><span class="attribute">c</span>=np.logspace(1,4,4,endpoint=True,base=2)</span><br></pre></td></tr></table></figure>
<h2 id="存取、切片"><a href="#存取、切片" class="headerlink" title="存取、切片**"></a>存取、切片**</h2><figure class="highlight stylus"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">#选取指定行/列</span><br><span class="line">a=np.arange(<span class="number">1</span>,<span class="number">10</span>)</span><br><span class="line"><span class="function"><span class="title">print</span><span class="params">(<span class="string">'a='</span>,a)</span></span></span><br><span class="line">#获取某个元素</span><br><span class="line"><span class="function"><span class="title">print</span><span class="params">(<span class="string">'a[3]='</span>,a[<span class="number">3</span>])</span></span></span><br><span class="line">#获取第<span class="number">3</span>-<span class="number">6</span>个元素，左必右开</span><br><span class="line"><span class="function"><span class="title">print</span><span class="params">(<span class="string">'a[3:6]='</span>,a[<span class="number">3</span>:<span class="number">6</span>])</span></span></span><br><span class="line">#省略开始下标，表示从<span class="number">0</span>开始</span><br><span class="line"><span class="function"><span class="title">print</span><span class="params">(<span class="string">'a[:]='</span>,a[:<span class="number">5</span>])</span></span></span><br><span class="line">#步长为<span class="number">2</span></span><br><span class="line"><span class="function"><span class="title">print</span><span class="params">(<span class="string">'a[1:9:2]='</span>,a[<span class="number">1</span>:<span class="number">9</span>:<span class="number">2</span>])</span></span></span><br><span class="line">#步长为-<span class="number">1</span>，即翻转</span><br><span class="line"><span class="function"><span class="title">print</span><span class="params">(<span class="string">'a[::-1]='</span>,a[::-<span class="number">1</span>])</span></span></span><br><span class="line">#切片数据是原数组的一个视图，与原数组共享内容空间</span><br><span class="line"><span class="selector-tag">b</span> = <span class="selector-tag">a</span>[<span class="number">2</span>:<span class="number">5</span>]</span><br><span class="line"><span class="selector-tag">b</span>[<span class="number">0</span>] = <span class="number">200</span></span><br><span class="line"><span class="function"><span class="title">print</span><span class="params">(a)</span></span></span><br></pre></td></tr></table></figure>
<h2 id="随机生成"><a href="#随机生成" class="headerlink" title="随机生成**"></a>随机生成**</h2><figure class="highlight processing"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br></pre></td><td class="code"><pre><span class="line">#均匀分布的随机数</span><br><span class="line">a=np.<span class="built_in">random</span>.rand(<span class="number">10</span>)</span><br><span class="line">#指定<span class="built_in">shape</span></span><br><span class="line">b = np.<span class="built_in">random</span>.rand(<span class="number">3</span>,<span class="number">2</span>)</span><br><span class="line"><span class="built_in">print</span>(<span class="string">'a= '</span>,a)</span><br><span class="line"><span class="built_in">print</span>(<span class="string">'b= \n'</span>,b)</span><br><span class="line">#正态分布的随机数, eg.N(<span class="number">3</span>, <span class="number">6.25</span>)</span><br><span class="line">c = <span class="number">2.5</span> * np.<span class="built_in">random</span>.randn(<span class="number">2</span>, <span class="number">4</span>) + <span class="number">3</span></span><br><span class="line"><span class="built_in">print</span>(<span class="string">'c= '</span>,c)</span><br><span class="line">#<span class="number">0</span><span class="number">-4</span>整数</span><br><span class="line">d = np.<span class="built_in">random</span>.randint(<span class="number">5</span>, <span class="built_in">size</span>=(<span class="number">2</span>, <span class="number">4</span>))</span><br><span class="line"><span class="built_in">print</span>(<span class="string">'d= \n'</span>,d)</span><br><span class="line">#洗牌</span><br><span class="line">e= np.arange(<span class="number">10</span>)</span><br><span class="line"><span class="built_in">print</span>(<span class="string">'e= '</span>,e)</span><br><span class="line">np.<span class="built_in">random</span>.shuffle(e)</span><br><span class="line"><span class="built_in">print</span>(<span class="string">'e= '</span>,e)</span><br></pre></td></tr></table></figure>
<h2 id="使用bool数组存取"><a href="#使用bool数组存取" class="headerlink" title="使用bool数组存取**"></a>使用<strong><strong>bool</strong></strong>数组存取**</h2><figure class="highlight stylus"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br></pre></td><td class="code"><pre><span class="line">#大于<span class="number">0.5</span>的元素索引</span><br><span class="line">print (<span class="selector-tag">a</span> > <span class="number">0.5</span>)</span><br><span class="line"></span><br><span class="line">#大于<span class="number">0.5</span>的元素</span><br><span class="line"><span class="selector-tag">b</span> = <span class="selector-tag">a</span>[<span class="selector-tag">a</span> > <span class="number">0.5</span>]</span><br><span class="line"><span class="function"><span class="title">print</span><span class="params">(<span class="string">'b= '</span>,b)</span></span></span><br><span class="line"></span><br><span class="line">#将数组b中大于<span class="number">0.5</span>的元素截取成<span class="number">0.5</span></span><br><span class="line"><span class="selector-tag">b</span>[<span class="selector-tag">b</span> > <span class="number">0.5</span>] = <span class="number">0.5</span></span><br><span class="line"><span class="function"><span class="title">print</span><span class="params">(<span class="string">'b= '</span>,b)</span></span></span><br><span class="line"></span><br><span class="line">#a不受影响，此处a和b不共享内存</span><br><span class="line"><span class="function"><span class="title">print</span><span class="params">(<span class="string">'a= '</span>,a)</span></span></span><br></pre></td></tr></table></figure>
<h2 id="计算（点乘、求和…）"><a href="#计算（点乘、求和…）" class="headerlink" title="计算（点乘、求和…）**"></a>计算（点乘、求和…）**</h2><figure class="highlight routeros"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br></pre></td><td class="code"><pre><span class="line"><span class="comment">#创建矩阵A和B</span></span><br><span class="line"><span class="attribute">A</span>=np.array([[1,1],[0,1]])</span><br><span class="line"><span class="attribute">B</span>=np.array([[2,0],[3,4]])</span><br><span class="line"></span><br><span class="line"><span class="comment">#元素相乘element-wiseproduct</span></span><br><span class="line">A<span class="number">*B</span></span><br><span class="line"></span><br><span class="line"><span class="comment">#点乘</span></span><br><span class="line">A.dot(B)</span><br><span class="line">np.dot(A,B)</span><br><span class="line"></span><br><span class="line"><span class="comment">#求和</span></span><br><span class="line">B.sum(<span class="attribute">axis</span>=1)</span><br><span class="line">B.sum(<span class="attribute">axis</span>=1,keepdims=True)</span><br><span class="line"><span class="comment">#max,min,sqrt,exp...</span></span><br></pre></td></tr></table></figure>
<h2 id="meshgrid"><a href="#meshgrid" class="headerlink" title="meshgrid**"></a>meshgrid**</h2><figure class="highlight lsl"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br></pre></td><td class="code"><pre><span class="line">import math</span><br><span class="line">import matplotlib as mpl</span><br><span class="line">import matplotlib.pyplot as plt</span><br><span class="line">from matplotlib import cm</span><br><span class="line">from mpl_toolkits.mplot3d import Axes3D</span><br><span class="line"></span><br><span class="line">#meshgrid用于从数组a和b产生网格</span><br><span class="line">u = np.linspace(<span class="number">-3</span>, <span class="number">3</span>, <span class="number">101</span>)</span><br><span class="line">x, y = np.meshgrid(u, u)</span><br><span class="line"></span><br><span class="line">z = x*y*np.exp(-(x**<span class="number">2</span> + y**<span class="number">2</span>)/<span class="number">2</span>) / math.sqrt(<span class="number">2</span>*math.pi)</span><br><span class="line">fig = plt.figure()</span><br><span class="line">ax = fig.add_subplot(<span class="number">111</span>, projection='<span class="number">3</span>d')</span><br><span class="line">ax.plot_surface(x, y, z, cmap=cm.coolwarm, linewidth=<span class="number">0.1</span>) </span><br><span class="line"></span><br><span class="line">#eg</span><br><span class="line">np.arange(<span class="number">0</span>,<span class="number">60</span>,<span class="number">10</span>).reshape((<span class="number">-1</span>,<span class="number">1</span>))+np.arange(<span class="number">6</span>)</span><br><span class="line">array([[ <span class="number">0</span>, <span class="number">1</span>, <span class="number">2</span>, <span class="number">3</span>, <span class="number">4</span>, <span class="number">5</span>],</span><br><span class="line"> [<span class="number">10</span>, <span class="number">11</span>, <span class="number">12</span>, <span class="number">13</span>, <span class="number">14</span>, <span class="number">15</span>],</span><br><span class="line"> [<span class="number">20</span>, <span class="number">21</span>, <span class="number">22</span>, <span class="number">23</span>, <span class="number">24</span>, <span class="number">25</span>],</span><br><span class="line"> [<span class="number">30</span>, <span class="number">31</span>, <span class="number">32</span>, <span class="number">33</span>, <span class="number">34</span>, <span class="number">35</span>],</span><br><span class="line"> [<span class="number">40</span>, <span class="number">41</span>, <span class="number">42</span>, <span class="number">43</span>, <span class="number">44</span>, <span class="number">45</span>],</span><br><span class="line"> [<span class="number">50</span>, <span class="number">51</span>, <span class="number">52</span>, <span class="number">53</span>, <span class="number">54</span>, <span class="number">55</span>]])</span><br></pre></td></tr></table></figure>
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<div class="post-toc-content"><ol class="nav"><li class="nav-item nav-level-2"><a class="nav-link" href="#使用array创建矩阵"><span class="nav-number">1.</span> <span class="nav-text">使用array创建矩阵</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#使用函数创建矩阵"><span class="nav-number">2.</span> <span class="nav-text">使用函数创建矩阵**</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#存取、切片"><span class="nav-number">3.</span> <span class="nav-text">存取、切片**</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#随机生成"><span class="nav-number">4.</span> <span class="nav-text">随机生成**</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#使用bool数组存取"><span class="nav-number">5.</span> <span class="nav-text">使用bool数组存取**</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#计算（点乘、求和…）"><span class="nav-number">6.</span> <span class="nav-text">计算（点乘、求和…）**</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#meshgrid"><span class="nav-number">7.</span> <span class="nav-text">meshgrid**</span></a></li></ol></div>
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