\documentclass{article}
\usepackage[active,tightpage]{preview}
\usepackage{varwidth}
\usepackage{pgfplots}
\begin{document}
\begin{preview}
\begin{varwidth}{\linewidth}
\centering
\begin{tikzpicture}
\begin{axis}[ 
	title = \textbf{k-NN},
	xlabel=Number of extracted features, 
	ylabel=Accuracy,
	grid=both,
 	height=5cm, width=8.0cm, 
 	legend pos=south east, 
 	minor tick num = 1,
	xtick={1, 2, 3, 4},
	cycle list={{gray,line width=1.5pt},{black,line width=1.5pt},}
	]
\addplot+[error bars/.cd, x dir=none, x fixed relative=0.5, y dir=both,y explicit relative,]
table[x=features,y=PCA,y error=PCA_conf]{
features	PCA	PCA_conf	BDPC	BDPC_conf
1	0.688396	0.005072	0.671337	0.005321
2	0.693422	0.004881	0.680882	0.005181
3	0.697166	0.005061	0.693209	0.005065
4	0.697166	0.005061	0.697193	0.005050
};
\addplot+[error bars/.cd,
x dir=none, x fixed relative=0.5,
y dir=both,y explicit relative,
]
table[x=features,y=BDPC,y error=BDPC_conf]{
features	PCA	PCA_conf	BDPC	BDPC_conf
1	0.688396	0.005072	0.671337	0.005321
2	0.693422	0.004881	0.680882	0.005181
3	0.697166	0.005061	0.693209	0.005065
4	0.697166	0.005061	0.697193	0.005050
};
\legend{PCA, Proposed}
\end{axis}
\end{tikzpicture}
\end{varwidth}
\end{preview}
\end{document}
