Tabularx can't center some column

Question

I'm trying to create a timetable using tabularx environment, but i can't find a way to center all columns.

Using this code:

\documentclass[11pt,oneside, landscape]{article} 

\usepackage[utf8]{inputenc} 

\usepackage{geometry}
\geometry{a4paper} 
\usepackage[osf]{mathpazo}
\linespread{1.05}\selectfont 

\usepackage{graphicx}
\usepackage[dvipsnames]{xcolor}  


\usepackage{booktabs}
\usepackage{array} 

\usepackage{tabularx}

\usepackage{fancyhdr}
\pagestyle{empty}

\newcommand{\tit}[1]{\fontsize{15}{17}\color{darkgray}\usefont{T1}{pplj}{b}{it}\selectfont #1}

\begin{document}

\begin{center}
\renewcommand{\arraystretch}{1.5}

\begin{tabularx}{19cm}{r >{\centering}X >{\centering}X >{\centering}X >{\centering}X X}
                   & \tit{Lun} &  \tit{Mar} &  \tit{Mer} & \tit{Gio} & \tit{Ven} \\
\toprule
\color{gray}9-11  $||$ &  & Laboratorio III &  &  Metodi mat. per la fisica & Laboratorio III \\ \midrule
\color{gray}11-13  $||$& Meccanica Quantistica & Metodi mat. per la fisica &  & Meccanica Quantistica & Fisica dell'informazione \\ \midrule
\midrule
\color{gray}15-17  $||$ &  & Fisica dell'informazione & Laboratorio III &  & \\
\bottomrule

\end{tabularx}

\end{center}

\end{document}

i get this

where last column is not centered. If i try to change

\begin{tabularx}{19cm}{r >{\centering}X >{\centering}X >{\centering}X >{\centering}X X}

with

\begin{tabularx}{19cm}{r >{\centering}X >{\centering}X >{\centering}X >{\centering}X {\centering}X}

i get

! Misplaced \noalign.
\toprule ->\noalign 
                    {\ifnum 0=`}\fi \@aboverulesep =\abovetopsep \global        \@b...
l.39 \end{tabularx}

Answer 1

Both the package arrayand the the package tabularxredefine \\ in a slightly different way. I refer to tabularx-can’t-center-some-column for a more in depth explanation.

When defining the last column, you have to put in an \arraybackslash after the \centering-command, i.e.:

>{\centering\arraybackslash}X

Your table preamble will be:

\begin{tabularx}{19cm}{r >{\centering}X >{\centering}X%
>{\centering}X >{\centering}X >{\centering\arraybackslash}X}

Or you can use tabu:

\documentclass[11pt,oneside, landscape]{article} 
\usepackage[utf8]{inputenc} 
\usepackage{geometry}
\geometry{a4paper} 
\usepackage[osf]{mathpazo}
\linespread{1.05}\selectfont 
\usepackage{graphicx,tabu}
\usepackage[dvipsnames]{xcolor}  
\usepackage{booktabs}
\usepackage{array} 
\usepackage{tabularx}
\usepackage{fancyhdr}
\pagestyle{empty}

\newcommand{\tit}[1]{\fontsize{15}{17}\color{darkgray}\usefont{T1}{pplj}{b}{it}\selectfont #1}

\begin{document}
\tabulinesep=4pt

\begin{tabu}to 19cm{r X[c] X[c] X[c] X[c] X[c]}
\rowfont{\tit} & Lun &  Mar &  Mer & Gio & Ven \strut\\
\toprule
\color{gray}9-11  $||$ &  & Laboratorio III &  &  Metodi mat. per la fisica & Laboratorio III \\ \midrule
\color{gray}11-13  $||$& Meccanica Quantistica & Metodi mat. per la fisica &  & Meccanica Quantistica & Fisica dell'informazione \\\midrule
\midrule
\color{gray}15-17  $||$ &  & Fisica dell'informazione & Laboratorio III &  & \\
\bottomrule
\end{tabu}
\end{document}

MWE with tabu:

Answer 2

in preamble define new column type, for example:

\newcolumntype{C}{>{\centering\arraybackslash}X}

and then instead >{\centering}X and >{\centering\arraybackslash}X just use for column type C.