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<h3 class="section" id="Examples-1"><span>19.7 Examples<a class="copiable-link" href="#Examples-1"> ¶</a></span></h3>
<p>The following are examples of vectorization questions asked by actual
users of Octave and their solutions.
</p>
<ul class="itemize mark-bullet">
<li>For a vector <code class="code">A</code>, the following loop
<div class="example">
<div class="group"><pre class="example-preformatted">n = length (A) - 1;
B = zeros (n, 2);
for i = 1:n
## this will be two columns, the first is the difference and
## the second the mean of the two elements used for the diff.
B(i,:) = [A(i+1)-A(i), (A(i+1) + A(i))/2];
endfor
</pre></div></div>
<p>can be turned into the following one-liner:
</p>
<div class="example">
<pre class="example-preformatted">B = [diff(A)(:), 0.5*(A(1:end-1)+A(2:end))(:)]
</pre></div>
<p>Note the usage of colon indexing to flatten an intermediate result into
a column vector. This is a common vectorization trick.
</p>
</li></ul>
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