Allow [ characters in tables without entering math-mode (from R)

Your use of (snippet)

%...
[1, 5) &  2 \\
[5, 8) &  5 \\
%...

is interpreted (visually) as

%...
       &  1 \\[1, 5) 
       &  2 \\[5, 8)
       &  5 \\[5, 8)
%...

since LaTeX expects an optional argument after \\ to contain a length/dimension. The easiest work-around is to insert a non-[ after \\, like {} (an empty group). For example:

\begin{tabular}{D{.}{.}{7}D{.}{.}{7}}
  \toprule
  \multicolumn{1}{c}{x} & \multicolumn{1}{c}{y} \\
  \midrule
  {}[1, 5) &  1 \\
  {}[1, 5) &  2 \\
  {}[5, 8) &  5 \\
  {}[5, 8) &  7 \\
  {}[8,10] &  8 \\
  {}[8,10] & 10 \\
  \bottomrule
\end{tabular}

_{The first {} is not needed, but I've inserted it for a consistent look in the code.}