pgfplots relies extensively on key=value system. So initially it's a little frustrating to find the correct key. However, the basics are very easy to set up. For this particular example, there are various options that you have to set to match the given figure. Here is a starter :
\documentclass{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.7}
\begin{document}
{
% http://tex.stackexchange.com/questions/50313/everymath-and-set-font-for-math
\everymath{\mathsf{\xdef\mysf{\mathgroup\the\mathgroup\relax}}\mysf}
\begin{tikzpicture}[font=\sffamily]
\begin{semilogyaxis}[title=\textbf{QWS Dataset},
legend pos=outer north east,xtick={1,...,10},
scaled ticks=false,
log ticks with fixed point,
width=7cm,
ylabel = Computation Time (msec),
xlabel = Number of Service Candidates Per Class
]
\addplot plot coordinates {(2, 48)(3,336)(4,2048)(5, 11520)(6, 61440)(7,1315392)};
\addplot plot coordinates {(2, 37)(3, 275)(4,1726)(5, 9953)(6, 55387)(7, 297786)};
\addplot plot coordinates {(2, 43)(3,252)(4, 1421)(5, 7256)(6, 37561)(7,81679)};
\legend{Unreduced, Symmetric, Asymmetric}
\end{semilogyaxis}
\end{tikzpicture}
}
\end{document}

pgfplots. – percusse Nov 19 '12 at 15:37semilogyaxisenvironment. – percusse Nov 19 '12 at 15:56