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Basics.html
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<title>Basics</title>
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<h1 id="basic-eigen">Basic Eigen</h1>
<h2 id="initialising-a-matrixvector">Initialising a Matrix/Vector</h2>
<p>To create a Matrix of dimention <span class="math inline">\(\text{N}\times\text{M}\)</span> or a vector of dimension <span class="math inline">\(\text{N}\)</span> write</p>
<div class="sourceCode" id="cb1"><pre class="sourceCode cpp"><code class="sourceCode cpp"><a class="sourceLine" id="cb1-1" data-line-number="1"> Eigen::MatrixXd A(N,M)</a>
<a class="sourceLine" id="cb1-2" data-line-number="2"> Eigen::VectorXd v(N)</a></code></pre></div>
<p>The dimensions don’t have to be specified. If a Matrix of a different number-type is required, the <code>Matrix</code>-Template can be used. If the size is not known at compile-time, the row and column paramters can be set to <code>dynamic</code>.</p>
<div class="sourceCode" id="cb2"><pre class="sourceCode cpp"><code class="sourceCode cpp"><a class="sourceLine" id="cb2-1" data-line-number="1"> Eigen::Matrix<<span class="kw">typename</span> Scalar, <span class="dt">int</span> rows, <span class="dt">int</span> columns></a></code></pre></div>
<p>A random or constant Matrix can be created by the following commands respectively:</p>
<div class="sourceCode" id="cb3"><pre class="sourceCode cpp"><code class="sourceCode cpp"><a class="sourceLine" id="cb3-1" data-line-number="1"> Eigen::MatrixXd A = Eigen::MatrixXd::Random(N,M)</a>
<a class="sourceLine" id="cb3-2" data-line-number="2"> Eigen::MatrixXd A = Eigen::MatrixXd::Constant(N,M,c)</a></code></pre></div>
<h2 id="acessing-a-matrix">Acessing a Matrix</h2>
<p>The Matrices can be filled with the <code><<</code> command, where the filling is rowwise.</p>
<div class="sourceCode" id="cb4"><pre class="sourceCode cpp"><code class="sourceCode cpp"><a class="sourceLine" id="cb4-1" data-line-number="1"> Eigen::MatrixXd A(<span class="dv">2</span>,<span class="dv">3</span>);</a>
<a class="sourceLine" id="cb4-2" data-line-number="2"> A<<<span class="dv">1</span><<<span class="dv">2</span><<<span class="dv">3</span><<<span class="dv">4</span><<<span class="dv">5</span><<<span class="dv">6</span>;</a></code></pre></div>
<p>A Matrix-Element can by acessed by specifying its row and column, starting with 0. It can however also be accessed with index-based notation, where the default storage order is column-major.</p>
<div class="sourceCode" id="cb5"><pre class="sourceCode cpp"><code class="sourceCode cpp"><a class="sourceLine" id="cb5-1" data-line-number="1"> A(<span class="dv">0</span>,<span class="dv">0</span>)=<span class="dv">1</span>;</a>
<a class="sourceLine" id="cb5-2" data-line-number="2"> A(<span class="dv">1</span>,<span class="dv">0</span>)=<span class="dv">4</span>;</a></code></pre></div>
<h2 id="matrix-operations">Matrix-Operations</h2>
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