Group only some columns in latex - latex

Question

I want to do something like this:
It has two headings: the upper one I'm done with but now I want to add a lower heading for only some columns.
Is there a way to add such a heading in latex?
My attempt:
\begin{tabular}{lcccccccc}\hline \hline
& Whole world & Base sample & Whole world & Base sample & Whole world & Base sample & Whole world & Base sample \\
& (1) & (2) & (3) & (4) & (5) & (6) & (7) & (8) \\ \hline \\
& & & & & & & & & \\
\multicolumn{6}{c}{Dependent variable is log GDP per capita in 1995 } \\
& & & & & & & & \\

Answer 1

The following uses the eqparbox package to set the integer and decimal part of each number wrapped inside a \fmtnum
\documentclass{article}
\usepackage{booktabs,makecell,eqparbox}
\newcommand{\mc}{\multicolumn{1}{c}}
\makeatletter
\newcommand{\fmtnum}[1]{\#fmtnum#1\relax}
\def\#fmtnum#1.#2\relax{\eqmakebox[int][r]{$#1.$}\eqmakebox[dec][l]{$#2$}}
\makeatother
\begin{document}
\noindent
\begin{tabular}{ *{8}{c} }
\toprule
\makecell{Whole \\ world \\ (1)} &
\makecell{Base \\ sample \\ (2)} &
\makecell{Whole \\ world \\ (3)} &
\makecell{Base \\ sample \\ (4)} &
\makecell{Whole \\ world \\ (5)} &
\makecell{Base \\ sample \\ (6)} &
\makecell{Whole \\ world \\ (7)} &
\makecell{Base \\ sample \\ (8)} \\
\midrule
\multicolumn{6}{c}{\small Dependent variable is log GDP per capita in 1995} &
\multicolumn{2}{c}{\small \makecell[b]{Dependent variable \\ is log output per \\ worker in 1998}} \\
\cmidrule(lr){1-6}\cmidrule{7-8}
\fmtnum{ 0.54 } & \fmtnum{ 0.52 } & \fmtnum{ 0.47 } & \fmtnum{ 0.43 } & \fmtnum{ 0.47 } & \fmtnum{ 0.41 } & \fmtnum{ 0.45 } & \fmtnum{ 0.46 } \\
\fmtnum{(0.04)} & \fmtnum{(0.06)} & \fmtnum{(0.06)} & \fmtnum{(0.05)} & \fmtnum{(0.06)} & \fmtnum{(0.06)} & \fmtnum{(0.04)} & \fmtnum{(0.06)} \\
\addlinespace
& & \fmtnum{ 0.89 } & \fmtnum{ 0.37 } & \fmtnum{ 1.60 } & \fmtnum{ 0.92 } \\
& & \fmtnum{(0.49)} & \fmtnum{(0.51)} & \fmtnum{(0.70)} & \fmtnum{(0.63)} \\
& & & \fmtnum{-0.62 } & & \fmtnum{-0.60 } \\
& & & \fmtnum{(0.19)} & & \fmtnum{(0.23)} \\
& & & \fmtnum{-1.00 } & & \fmtnum{-0.90 } \\
& & & \fmtnum{(0.15)} & & \fmtnum{(0.17)} \\
& & & \fmtnum{-0.25 } & & \fmtnum{-0.04 } \\
& & & \fmtnum{(0.20)} & & \fmtnum{(0.32)} \\
\fmtnum{ 0.62 } & \fmtnum{ 0.54 } & \fmtnum{ 0.63 } & \fmtnum{ 0.73 } & \fmtnum{ 0.56 } & \fmtnum{ 0.69 } & \fmtnum{ 0.55 } & \fmtnum{ 0.49 } \\
\mc{110} & \mc{64} & \mc{110} & \mc{110} & \mc{64} & \mc{64} & \mc{108} & \mc{61} \\
\bottomrule
\end{tabular}
\end{document}
While it is a bit cumbersome, there is very little uniformity across the table, with mixtures of decimal values using parentheses and negative numbers, numbers without decimal parts and also headers that are wider than their column constituents (columns 7-8).
The above code requires at least 2 compilations with every change in the maximum width of a number's integer or decimal part.
You can streamline the input a little using collcell:
\documentclass{article}
\usepackage{booktabs,makecell,eqparbox,collcell}
\newcommand{\mc}{\multicolumn{1}{c}}
\makeatletter
\newcommand{\fmtnum}[1]{\if\relax\detokenize{#1}\relax\else\#fmtnum#1\relax\fi}
\def\#fmtnum#1.#2\relax{\eqmakebox[int][r]{$#1.$}\eqmakebox[dec][l]{$#2$}}
\makeatother
\begin{document}
\noindent
\begin{tabular}{ *{8}{>{\collectcell\fmtnum}c<{\endcollectcell}} }
\toprule
\mc{\makecell{Whole \\ world \\ (1)}} &
\mc{\makecell{Base \\ sample \\ (2)}} &
\mc{\makecell{Whole \\ world \\ (3)}} &
\mc{\makecell{Base \\ sample \\ (4)}} &
\mc{\makecell{Whole \\ world \\ (5)}} &
\mc{\makecell{Base \\ sample \\ (6)}} &
\mc{\makecell{Whole \\ world \\ (7)}} &
\mc{\makecell{Base \\ sample \\ (8)}} \\
\midrule
\multicolumn{6}{c}{\small Dependent variable is log GDP per capita in 1995} &
\multicolumn{2}{c}{\small \makecell[b]{Dependent variable \\ is log output per \\ worker in 1998}} \\
\cmidrule(lr){1-6}\cmidrule{7-8}
0.54 & 0.52 & 0.47 & 0.43 & 0.47 & 0.41 & 0.45 & 0.46 \\
(0.04) & (0.06) & (0.06) & (0.05) & (0.06) & (0.06) & (0.04) & (0.06) \\
\addlinespace
& & 0.89 & 0.37 & 1.60 & 0.92 \\
& & (0.49) & (0.51) & (0.70) & (0.63) \\
& & & -0.62 & & -0.60 \\
& & & (0.19) & & (0.23) \\
& & & -1.00 & & -0.90 \\
& & & (0.15) & & (0.17) \\
& & & -0.25 & & -0.04 \\
& & & (0.20) & & (0.32) \\
0.62 & 0.54 & 0.63 & 0.73 & 0.56 & 0.69 & 0.55 & 0.49 \\
\mc{110} & \mc{64} & \mc{110} & \mc{110} & \mc{64} & \mc{64} & \mc{108} & \mc{61} \\
\bottomrule
\end{tabular}
\end{document}