What is the best way to produce TikZ picture for discrete signals?

Question

I would like to draw discrete signals, as shown in the illustration below, but not by way of drawings of individual lines.gnuplot could be used for this work? It would be nice to be able to choose the sampling period, or something similar.

Answer 1

Using TikZ and pgfplots the best option is adding ycomb to your plot, as follows:

\documentclass{article}
\usepackage{tikz,pgfplots}%http://www.ctan.org/pkg/pgf http://www.ctan.org/pkg/pgfplots
\begin{document}
    \pgfplotsset{
    standard/.style={%Axis format configuration
        axis x line=middle,
        axis y line=middle,
        enlarge x limits=0.15,
        enlarge y limits=0.15,
        every axis x label/.style={at={(current axis.right of origin)},anchor=north west},
        every axis y label/.style={at={(current axis.above origin)},anchor=north east},
        every axis plot post/.style={mark options={fill=white}}
        }
    }
    \begin{figure}%Unit step squence
        \begin{tikzpicture}
            \begin{axis}[%
                standard,
                domain = 0:15,
                samples = 16,
                xlabel={$n$},
                ylabel={$\mu[n]$},
                ymin=0,
                ymax=1.5]
                \addplot+[ycomb,black,thick] {1};
            \end{axis}
        \end{tikzpicture}
    \end{figure}

    \begin{figure}%Sampled sine squence
        \begin{tikzpicture}
            \begin{axis}[%
                standard,
                domain = 0:15,
                samples = 16,
                xlabel={$n$},
                ylabel={$x[n]$}]
                \addplot+[ycomb,black,thick] {sin(2*180*x/13)};
            \end{axis}
        \end{tikzpicture}
    \end{figure} 
\end{document}

The result:

Possibly you can improve the look, might be tedious but add a sequence always easy.

Answer 2

The first function

\documentclass[pstricks,border=12pt]{standalone}
\usepackage{pst-plot,pst-node}
\begin{document}
\psset{xunit=.5}
\begin{pspicture}(-1,-.5)(16.5,2)
    \psaxes[Dy=.5]{->}(0,0)(-.9,0)(16,1.5)[$n$,0][$l[n]$,90]
    \curvepnodes[plotpoints=16]{0}{15}{t 1}{A}
    \psset{linecolor=red}
    \multido{\i=0+1}{\numexpr\Anodecount+1}{\psline{-o}(!\i\space dt mul 0)(A\i)}
\end{pspicture}
\end{document}

The second function

\documentclass[pstricks,border=12pt]{standalone}
\usepackage{pst-plot,pst-node}
\begin{document}
\psset{xunit=.5}
\makeatletter
\begin{pspicture}(-1,-1.)(16.5,2)
    \psaxes[Dy=.5,labels=y,ticks=y]{->}(0,0)(-.9,0)(16,1.5)[$n$,0][$x[n]$,90]
    \degrees[13]
    \curvepnodes[plotpoints=16]{0}{15}{t t \pst@angleunit sin}{A}
    \psset{linecolor=red}
    \multido{\i=0+1}{\numexpr\Anodecount+1}
    {
        \psline{-o}(!\i\space dt mul 0)(A\i)
        \psxTick[xlabelsep=\ifnum \ifnum\i<13 \i \else 0 \fi > 7 -17 \else 5\fi pt](\i){$\i$}
    }
\end{pspicture}
\makeatother
\end{document}

Answer 3

Although not exact solution, but using gnuplottex as mentioned in your Q. In anycase, pgfplots would always be best for this task.

% Need "-shell-escape" enabled and gnuplot 4.4 
\documentclass[preview=true,12pt,border=5pt]{standalone}
\usepackage{gnuplottex} 
\begin{document} 
\begin{gnuplot}[terminal=epslatex,terminaloptions=color]
unset border
set samples 16 #  no of sampling points
set xtics 1 nomirror # custom tick marks and labels
set ytics 0.5 nomirror 
set xlabel '$n$'
set ylabel '$\mu[n]$'
xmin=0;xmax=15;ymin=0;ymax=1; # co-ordinates of xaxis and yaxis
set arrow from xmin-0.05,ymin to xmax+0.9,ymin lt -1 lw 4 # x-axis 
set arrow from  xmin,ymax to  xmin,ymax+0.15 lt -1 lw 4  # y-axis
set arrow from 8,ymin-0.14 to 10,ymin-0.14 #x-axis label arrow
set arrow from xmin-2.2,0.65 to xmin-2.2 ,0.8 #y-axis label arrow
plot [0:15]  [0:1.1 ] 1 with impulses lt -1 lw 4 notitle ,1.02 with  points ps 3 pt 6 lt 3  lw 4 lc rgb 'black' notitle
# plot discrete signal first "with impulses " and then circular markers at discrete locations  
# "with linespoints "
\end{gnuplot} 
\end{document}

% Need "-shell-escape" enabled and gnuplot 4.4
\documentclass[preview=true,12pt,border=5pt]{standalone}
\usepackage{gnuplottex} 
\begin{document} 
\begin{gnuplot}[terminal=epslatex,terminaloptions=color]
unset border
set xzeroaxis # set zero xaxis
set xtics axis # move the xaxis tick lables to center
set xtics 2 offset 0.55,1.75 nomirror # custom tick marks and labels
unset ytics
set ytics ("0.5" 0.5, "1" 1) nomirror
set samples 16 #  no of sampling points
set xlabel '$n$' offset  18, 9.5
set ylabel '$x[n]$' 
xmin=0;xmax=15;ymin=-1;ymax=1; # co-ordinates of xaxis and yaxis
set arrow from xmin-0.05,0 to xmax+0.9,0 lt -1 lw 4 # x-axis 
set arrow from  xmin,0 to  xmin,ymax+0.15 lt -1 lw 4  # y-axis
set arrow from 14,-0.15 to 16,-0.15 #x-axis label arrow
set arrow from xmin-2,0.2 to xmin-2 ,0.5 #y-axis label arrow
plot [0:15] [-1.1:1.1] sin(2*pi*x/13) with impulses lt -1 lw 4 notitle, sin(2*pi*x/13)+.00 with points ps 3 pt 6 lt -1 lw 4 lc rgb 'black' notitle
\end{gnuplot} 
\end{document}

Answer 4

and another PSTricks solution:

\documentclass[pstricks,border=12pt]{standalone}
\usepackage{pst-plot}
\begin{document}

\begin{pspicture}(-1,-1.)(8.5,2)
\psaxes[Dy=.5,labels=y,ticks=y]{->}(0,0)(-.9,0)(7.5,1.5)[$n$,0][$x[n]$,90]
\psplot[plotpoints=16,plotstyle=LineToXAxis,linecolor=red,
        showpoints,dotstyle=o,dotscale=2,algebraic]{0}{7}{0.9}
\end{pspicture}

\begin{pspicture}(-1,-1.)(8.5,2)
\psaxes[Dy=.5,labels=y,ticks=y]{->}(0,0)(-.9,0)(7.5,1.5)[$n$,0][$x[n]$,90]
\psplot[plotpoints=16,plotstyle=LineToXAxis,
        showpoints,dotstyle=o,dotscale=2,algebraic]{0}{7}{0.9*sin(x)}
\end{pspicture}

\end{document}