I would like to have my numbers aligned left but centered in a table as in this solution, which I also tried to apply. Now my numbers are of the form ~24%. For a correct alignment I tried to protect the non-number parts by writing it as {$\sim$}24{ \%}. The % is well behind the number, however the ~ is centered in the column and overlapping the numbers. Same thing happens when using something like {xx}60{ \%} where now the xx and the numbers overlap. How to protect the ~ to stay left of the number?
\documentclass{article}
\usepackage{booktabs,siunitx}
\begin{document}
\begin{tabular}{lS[table-format=2.0]S[table-format=2.0]}
\toprule
& {Before treatment} & {After treatment} \\
\midrule
component1 & {$\sim$}60{ \%} & {$\sim$}15{ \%} \\
component2 & {$\sim$}14{ \%} & {$\sim$}4{ \%} \\
component3 & {$\sim$}26{ \%} & {$\sim$}81{ \%} \\
\bottomrule
\end{tabular}
\end{document}

table-space-text-*options. Can you provide a sample table? For\simfor a~, please see How does one insert a backslash or a tilde (~) into LaTeX? On that note,\simis also allowed as input-comparator so it shouldn’t be a problem if you properly declare the comparator usage for that column. – Qrrbrbirlbel Nov 18 '13 at 16:32