\documentclass[border={10pt}]{standalone}
\usepackage{tikz,pgfplots,filecontents,amsmath}
\pgfplotsset{compat=1.5}

\begin{filecontents}{dataX.dat}
 n   xn
 0   1.0 
 1   2.0  
 2   3.0  
 3   2.0  
 4   1.0 
 5   1.0
 6   1.0
 7   1.0
 8   1.0
 9   1.0
 10  1.0
\end{filecontents}

\begin{filecontents}{dataY.dat}
	n   yn
	0   2.0 
	1   1.0  
	2   2.0  
	3   -1.0 
	4   2.0 
	5   3.0
	6   1.0
	7   1.0
	8   1.0
	9   1.0
	10  1.0
\end{filecontents}

\begin{document}

\begin{tikzpicture}
\begin{axis}
[%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    axis x line=middle,
    axis y line=middle,
    every axis x label={at={(current axis.right of origin)},anchor=north west},
    every axis y label={at={(current axis.above origin)},anchor= north west},
    every axis plot post/.style={mark options={fill=black}},
    xlabel={$n$},
    ylabel={$\boldsymbol{x[n]}$},
    xtick={0,2,...,10},
    ymin=-1,
    ymax=3,
]%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\addplot+[ycomb,black,thick] table [x={n}, y={xn}] {dataX.dat};
\end{axis}
\end{tikzpicture}
\begin{tikzpicture}
\begin{axis}
[%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
axis x line=middle,
axis y line=middle,
every axis x label={at={(current axis.right of origin)},anchor=north west},
every axis y label={at={(current axis.above origin)},anchor= north west},
every axis plot post/.style={mark options={fill=black}},
xlabel={$n$},
ylabel={$\boldsymbol{y[n]}$},
xtick={0,2,...,10},
ymin=-1,
ymax=3,
]%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\addplot+[ycomb,black,thick] table [x={n}, y={yn}] {dataY.dat};
\end{axis}
\end{tikzpicture}


\end{document}