\section{ISINF Test for infinities}

\subsection{Usage}

Returns true for entries of an array that are infs (i.e.,
infinities).  The usage is
\begin{verbatim}
   y = isinf(x)
\end{verbatim}
The result is a logical array of the same size as \verb|x|,
which is true if \verb|x| is not-a-number, and false otherwise.
Note that for \verb|complex| or \verb|dcomplex| data types that
the result is true if either the real or imaginary parts
are infinite.
\subsection{Example}

Suppose we have an array of floats with one element that
is \verb|inf|:
\begin{verbatim}
--> a = [1.2 3.4 inf 5]
a = 
  <double>  - size: [1 4]
 
Columns 1 to 4
   1.2    3.4    inf    5.0  
--> isinf(a)
ans = 
  <logical>  - size: [1 4]
 
Columns 1 to 4
 0  0  1  0  
--> b = 3./[2 5 0 3 1]
b = 
  <double>  - size: [1 5]
 
Columns 1 to 5
   1.5    0.6    inf    1.0    3.0  

\end{verbatim}
