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<div class="textblock"><p>Section: <a class="el" href="sec_array.html">Array Generation and Manipulations</a> </p>
<h1><a class="anchor" id="Usage"></a>
Usage</h1>
<p>The <code>diag</code> function is used to either construct a diagonal matrix from a vector, or return the diagonal elements of a matrix as a vector. The general syntax for its use is </p>
<pre class="fragment"> y = diag(x,n)
</pre><p> If <code>x</code> is a matrix, then <code>y</code> returns the <code>n</code>-th diagonal. If <code>n</code> is omitted, it is assumed to be zero. Conversely, if <code>x</code> is a vector, then <code>y</code> is a matrix with <code>x</code> set to the <code>n</code>-th diagonal. </p>
<h1><a class="anchor" id="Examples"></a>
Examples</h1>
<p>Here is an example of <code>diag</code> being used to extract a diagonal from a matrix.</p>
<pre class="fragment">--> A = int32(10*rand(4,5))
A =
5 8 8 3 6
4 8 4 3 7
9 5 8 4 2
1 0 10 0 4
--> diag(A)
ans =
5
8
8
0
--> diag(A,1)
ans =
8
4
4
4
</pre><p>Here is an example of the second form of <code>diag</code>, being used to construct a diagonal matrix.</p>
<pre class="fragment">--> x = int32(10*rand(1,3))
x =
6 3 9
--> diag(x)
ans =
6 0 0
0 3 0
0 0 9
--> diag(x,-1)
ans =
0 0 0 0
6 0 0 0
0 3 0 0
0 0 9 0
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