# xlog scale with pgfplots for random x-values

in the code below, two things should be modified:

1. xlabels and xgrid should appear for x=10^-0.1, x=10^0 and x=10^0.1 only
2. the grid along the x-axis should reflect the logarithmic scale (ie, not constant) with the major grid for the values listed above only

MWE:

\documentclass[12pt]{book}
\usepackage{tikz,pgfplots}
\pgfplotsset{compat=1.3,width=10cm}
\pgfkeys{/pgf/number format/.cd,set decimal separator={,}}
\begin{document}
\begin{tikzpicture}
\begin{semilogxaxis}[grid=both,enlarge x limits=false,scale only axis,width=8.5cm,height=6cm,ymin=1,ymax=1.5,tick style={draw=none}]
coordinates{(0.666667,1.21982)(1.49206,1.19949)};
\end{semilogxaxis}
\end{tikzpicture}
\end{document}

-

I think the option xtickten={-0.1,0,0.1} does what you want for both, (1.) and (2.): it displays only the tick positions 10^-0.1, 10^0 and 10^0.1 and it only displays these grid lines.
By default, pgfplots generates minor logarithmic grids only if the major ticks are of type j*10^j. Try out the minor xtick={<positions>} feature to provide some manually (requires a recent version I believe). Providing only the exponents base ten (like xtickten) is not possible here, however. –  Christian Feuersänger Aug 7 '11 at 13:12