We have provided some useful elements to expose basic interactive functionality for an end user. The first of these is the {\tt slider} command. 


Arguments for the {\tt slider} command are:

\begin{verbatim}
 \slider{min}{max}{variable}{latex}{default}
\end{verbatim}

The min and max values are for specifying the minimum and maximum of the range of the slider. 


The {\tt latex} argument is what to display next to the slider to indicate to the end user what variable the slider is changing. Finally, the most important is the {\tt variable} argument. The {\tt variable} specifies the variable that is changed based on the values of the slider, and can be used in the equations of {\tt psplot} commands. 


Note that using these ``extended'' features are not backwards compatible, a.k.a they don't work on paper!

\begin{interactive}
\psset{unit=1cm}

\begin{center}
\begin{pspicture}(-3.5,-1)(3.75,3.5)

\slider{1}{8}{n}{$N$}{4}

\psplot[algebraic,linewidth=1.5pt,plotpoints=1000]{-3.14}{3.14}{cos(n*x/2)+1.3}
\psaxes[showorigin=false,labels=none, Dx=1.62](0,0)(-3.25,0)(3.25,2.5)

\psline[linestyle=dashed](-3.14,0.3)(3.14,0.3)
\psline[linestyle=dashed](-3.14,2.3)(3.14,2.3)
\rput(3.6,2.3){$\frac{1}{1-\alpha}$}
\rput(3.6,0.3){$\frac{1}{1+\alpha}$}


\rput(3.14, -0.35){$\pi$}
\rput(1.62, -0.35){$\pi/2$}
\rput(-1.62, -0.35){$-\pi/2$}
\rput(-3.14, -0.35){$-\pi$}
\rput(0, -0.35){$0$}

\end{pspicture}
\end{center}
\end{interactive}


\begin{print}
\psset{unit=1cm}

\begin{center}
\begin{pspicture}(-3.5,-1)(3.75,3.5)

\psplot[algebraic,linewidth=1.5pt,plotpoints=1000]{-3.14}{3.14}{cos(4*x/2)+1.3}
\psaxes[showorigin=false,labels=none, Dx=1.62](0,0)(-3.25,0)(3.25,2.5)

\psline[linestyle=dashed](-3.14,0.3)(3.14,0.3)
\psline[linestyle=dashed](-3.14,2.3)(3.14,2.3)
\rput(3.6,2.3){$\frac{1}{1-\alpha}$}
\rput(3.6,0.3){$\frac{1}{1+\alpha}$}


\rput(3.14, -0.35){$\pi$}
\rput(1.62, -0.35){$\pi/2$}
\rput(-1.62, -0.35){$-\pi/2$}
\rput(-3.14, -0.35){$-\pi$}
\rput(0, -0.35){$0$}

\end{pspicture}
\end{center}
\end{print}

Which can be created using the following \TeX:


\begin{verbatim}
\begin{pspicture}(-3.5,-1)(3.75,3.5)

\slider{1}{8}{n}{$N$}{4}

\psplot[algebraic,linewidth=1.5pt,plotpoints=1000]{-3.14}{3.14}{cos(n*x/2)+1.3}
\psaxes[showorigin=false,labels=none, Dx=1.62](0,0)(-3.25,0)(3.25,2.5)
\psline[linestyle=dashed](-3.14,0.3)(3.14,0.3)
\psline[linestyle=dashed](-3.14,2.3)(3.14,2.3)
\rput(3.6,2.3){$\frac{1}{1-\alpha}$}
\rput(3.6,0.3){$\frac{1}{1+\alpha}$}
\rput(3.14, -0.35){$\pi$}
\rput(1.62, -0.35){$\pi/2$}
\rput(-1.62, -0.35){$-\pi/2$}
\rput(-3.14, -0.35){$-\pi$}
\rput(0, -0.35){$0$}
\end{pspicture}
\end{verbatim}




You can also add more than one slider (variable):

\begin{interactive}
\psset{unit=0.5cm}
\begin{center}
\begin{pspicture}(-13,-5)(13,10)

\slider{1}{8}{a}{amplitude}{4}
\slider{1}{8}{n}{frequency}{4}

\psplot[algebraic,linewidth=1.5pt,plotpoints=1000]{-12.56}{12.56}{a*sin(n*x)/(n*x)}
\psaxes[showorigin=false,labels=none, Dx=3.14](0,0)(-12.6,0)(12.6,0)

\rput(0, -0.5){$0$}

\end{pspicture}
\end{center}
\end{interactive}


\begin{print}
\psset{unit=0.5cm}
\begin{center}
\begin{pspicture}(-13,-5)(13,10)

\psplot[algebraic,linewidth=1.5pt,plotpoints=1000]{-12.56}{12.56}{4*sin(4*x)/(4*x)}
\psaxes[showorigin=false,labels=none, Dx=3.14](0,0)(-12.6,0)(12.6,0)

\rput(0, -0.5){$0$}

\end{pspicture}
\end{center}
\end{print}

which can be created with the following:

\begin{verbatim}
\begin{pspicture}(-13,-5)(13,10)
\slider{1}{8}{a}{amplitude}{4}
\slider{1}{8}{n}{frequency}{4}
\psplot[algebraic,linewidth=1.5pt,plotpoints=1000]{-12.56}{12.56}{a*sin(n*x)/(n*x)}
\psaxes[showorigin=false,labels=none, Dx=3.14](0,0)(-12.6,0)(12.6,0)
\rput(0, -0.5){$0$}
\end{pspicture}
\end{verbatim}
