rowcolor command from colortbl package leaves unwanted gaps in shading between columns

Question

I would like to highlight the first two rows of my table with a custom shade of gray. For this, I thought of using the \rowcolor environment from the colortbl package.

However, its usage seems to leave unwanted gaps in the shading, i.e. the shading patch does not get applied to the full row.

Here is a MWE

\documentclass{article}
\usepackage{xcolor}
\definecolor{newgray}{RGB}{196,196,196}
\usepackage{colortbl}
\usepackage{booktabs}
\usepackage{threeparttable}

\begin{document}
\begin{threeparttable}
    \centering
    \begin{tabular*}{\textwidth}{ l @{\extracolsep{\fill}} l c r}
        \multicolumn{4}{c}{\textbf{Random Table}} \\
        \toprule
        \multicolumn{1}{l}{Item} & \multicolumn{1}{l}{Case 1} & \multicolumn{1}{c}{Case 2} & \multicolumn{1}{r}{Case 3}\\
        \midrule

        \rowcolor{newgray}first thing, & \tnote{a}245  & \tnote{b}25e-6  & \tnote{c}79e-6 \\
        \rowcolor{newgray}[20pt][20pt]second thing & \tnote{a}450  & ---             & \tnote{b}24e-6 \\
        third thing                    & \tnote{d}2e-6 & \tnote{c}4123.5 & \tnote{b}2e-6  \\
        fourth thing                   & ---           & 1e6             & no data        \\
        \bottomrule
    \end{tabular*}
    \medskip
    \begin{tablenotes}
    \item[a] some explanation
    \item[b] this is why \dots
    \item[c] see reference awesome
    \item[d] hello world
    \item
    \end{tablenotes}
\end{threeparttable}
\end{document}

which produces the following output

Here are the requirements. I would like to have the table typeset to the textwidth achieved here using \begin{tabular*}{\textwidth}{ l @{\extracolsep{\fill}} l c r}, and secondly I need to have explanatory notes achieved here using the tablenotes environment provided by the threeparttable package. For aesthetics, I am using the booktabs package.

Clearly, the shading achieved right now is not desirable. When used without any overhang specification, the \rowcolor command leaves gaps in the shading. While, using left and right overhang minimises these shading gaps in the middle columns, it extends the shading beyond the table's width, which is undesirable.

How can I achieve the expected behavior, i.e. shade the row uniformly, with no gaps and without exceeding table's width?

Using tabularx to make the table span the textwidth does not seem to have this drawback. Would this be an option for you? — leandriis, May 28 '18 at 19:49
@leandriis I heard that there is no point in specifying X X X for all columns in tabularx. Maybe I am wrong. Anyway, I am curious to know your solution. — Dr Krishnakumar Gopalakrishnan, May 28 '18 at 19:50
@Krishna: My suggestion would have been what you already guessed: Using four X type columns. Here are also some related topics: color not applied properly in a row when \extraccolsep\fill is used in the tabular* environment and coloring entire row of tabular* — leandriis, May 28 '18 at 19:59
@leandriis the second link was very useful. Thank you. How would I use four X type columns and still retain the desired alignment of l l c r ? — Dr Krishnakumar Gopalakrishnan, May 28 '18 at 20:01
@Krishna: You can for example define your own column type based on the X type as shown here Centering in tabularx and X columns for a centered Xlike column. For raggedright or raggedleft alignment, this works analogously. — leandriis, May 28 '18 at 20:07
@leandriis that is awesome. However, the custom patch in the second link you referred me solved the issue for me. Many thanks for your help — Dr Krishnakumar Gopalakrishnan, May 28 '18 at 20:14

Zarko · Answer 1 · 2018-05-28T21:37:00.517

@{\extracolsep{\fill}} introduce additional space between columns which is not covered by rowcolor
in second line you have \rowcolor{newgray}[20pt][20pt] which should be only \rowcolor{newgray}
coloring rows and use rules from booktabs doesn't gives nice result, instead them i suggest lines provided by package boldline
for more vertical space in cells i suggest to use calspace

\documentclass{article}
\usepackage[table]{xcolor} % it call and enhance colortbl
\definecolor{newgray}{RGB}{196,196,196}
\usepackage{booktabs, threeparttable}
\usepackage{tabularx}       % new
\usepackage{boldline}       % new (part of shipunov bundle)
\usepackage{cellspace}      % new
\setlength\cellspacetoplimit{4pt}
\setlength\cellspacebottomlimit{4pt}
\addparagraphcolumntypes{X}
\newcolumntype{C}{>{\centering\arraybackslash}X}
\newcolumntype{L}{>{\raggedright\arraybackslash}X}
\newcolumntype{R}{>{\raggedleft\arraybackslash}X}

\begin{document}
\begin{threeparttable}
    \centering
\begin{tabularx}{\textwidth}{ S{>{\hsize=0.4\hsize}L}
                                >{\hsize=0.2\hsize}L
                                >{\hsize=0.2\hsize}C
                                >{\hsize=0.2\hsize}R}
\multicolumn{4}{c}{\textbf{Random Table}}                               \\
    \hlineB{2}
        Item    & Case 1        &   Case 2          &   Case 3          \\
    \hlineB{1.75}
    \rowcolor{newgray}
first thing,    & \tnote{a}245  & \tnote{b}25e-6    & \tnote{c}79e-6    \\
    \rowcolor{newgray}
second thing    & \tnote{a}450  & ---               & \tnote{b}24e-6    \\
third thing     & \tnote{d}2e-6 & \tnote{c}4123.5   & \tnote{b}2e-6     \\
fourth thing    & ---           & 1e6               & no data           \\
    \hlineB{2}
    \end{tabularx}

    \begin{tablenotes}
    \item[a] some explanation
    \item[b] this is why \dots
    \item[c] see reference awesome
    \item[d] hello world
    \item
    \end{tablenotes}
\end{threeparttable}
\end{document}

edit: if you like to have simpler solution with less nice table (which width is still equal to text width), than try the following:

\documentclass{article}
\usepackage[table]{xcolor}  % it call and enhance colortbl
\definecolor{newgray}{RGB}{196,196,196}
\usepackage{booktabs, threeparttable}
\usepackage{tabularx}       % new
\newcolumntype{C}{>{\centering\arraybackslash}X}
\newcolumntype{L}{>{\raggedright\arraybackslash}X}
\newcolumntype{R}{>{\raggedleft\arraybackslash}X}

\begin{document}
\begin{threeparttable}
    \centering
    \renewcommand\arraystretch{1.2}
\begin{tabularx}{\textwidth}{ L L C R }
\multicolumn{4}{c}{\textbf{Random Table}}                               \\
    \hline
        Item    & Case 1        &   Case 2          &   Case 3          \\
    \hline
    \rowcolor{newgray}
first thing,    & \tnote{a}245  & \tnote{b}25e-6    & \tnote{c}79e-6    \\
    \rowcolor{newgray}
second thing    & \tnote{a}450  & ---               & \tnote{b}24e-6    \\
third thing     & \tnote{d}2e-6 & \tnote{c}4123.5   & \tnote{b}2e-6     \\
fourth thing    & ---           & 1e6               & no data           \\
    \hline
\end{tabularx}

\begin{tablenotes}
\item[a] some explanation
\item[b] this is why \dots
\item[c] see reference awesome
\item[d] hello world
\item
\end{tablenotes}
\end{threeparttable}
\end{document}

note:

S{X} specifier means that to selected X column is added vertical space defined by
```
\setlength\cellspacetoplimit{4pt}
\setlength\cellspacebottomlimit{4pt}
```
with >{\hsize=0.4\hsize} and >{\hsize=0.2\hsize} is changed ratio between columns widths (first column has width equal 0.4\textwidth, other three have width equal 0.2\textwidth each)

the first solution can be simplified by removing cellspace stuff and for more vertical spaces around cells contents use simpler \renewcommand\arraystretch{1.2}:

\documentclass{article}
\usepackage[table]{xcolor} % it call and enhance colortbl
\definecolor{newgray}{RGB}{196,196,196}
\usepackage{booktabs, threeparttable}
\usepackage{tabularx}       % new
\usepackage{boldline}       % new (part of shipunov bundle)
\newcolumntype{C}{>{\centering\arraybackslash}X}
\newcolumntype{L}{>{\raggedright\arraybackslash}X}
\newcolumntype{R}{>{\raggedleft\arraybackslash}X}

\begin{document}
\begin{threeparttable}
    \centering
    \renewcommand\arraystretch{1.2}
\begin{tabularx}{\textwidth}{>{\hsize=0.4\hsize}L
                             >{\hsize=0.2\hsize}L
                             >{\hsize=0.2\hsize}C
                             >{\hsize=0.2\hsize}R}

 %% table body and table notes %%

\end{threeparttable}
\end{document}

it is not clear what the { S{>{\hsize=0.4\hsize}L} >{\hsize=0.2\hsize}L >{\hsize=0.2\hsize}C >{\hsize=0.2\hsize}R} commands are doing here. Can you provide a simpler example without using these commands ? — Dr Krishnakumar Gopalakrishnan, May 28 '18 at 21:09
it will become more clear after reading documentation for packages cellspace and tabularx :-). see edited answer. — Zarko, May 28 '18 at 21:39
thank you very much for the edits clarifying the question. Much appreciate your efforts. — Dr Krishnakumar Gopalakrishnan, May 29 '18 at 11:40

score 1 · Accepted Answer · answered Aug 16 '20 at 09:29

The environments {NiceTabular} and {NiceTabular*} of nicematrix provide tools to color cells, rows and columns without the drawbacks of colortbl.

Here, you have directly the expected result (but you need several commpilations).

\documentclass{article}
\usepackage{xcolor}
\usepackage{booktabs}
\usepackage{threeparttable}
\usepackage{nicematrix}
\begin{document}
\begin{threeparttable}
\centering
\begin{NiceTabular}{\textwidth}{ l @{\extracolsep{\fill}} l c r}%
  [code-before = \rowcolor[RGB]{196,196,196}{3,4}]
\multicolumn{4}{c}{\textbf{Random Table}} \
\toprule
\multicolumn{1}{l}{Item} & \multicolumn{1}{l}{Case 1} & \multicolumn{1}{c}{Case 2} & \multicolumn{1}{r}{Case 3}\
\midrule
first thing, & \tnote{a}245  & \tnote{b}25e-6  & \tnote{c}79e-6 \
second thing & \tnote{a}450  & ---             & \tnote{b}24e-6 \
third thing                    & \tnote{d}2e-6 & \tnote{c}4123.5 & \tnote{b}2e-6  \
fourth thing                   & ---           & 1e6             & no data        \
\bottomrule
\end{NiceTabular}
\medskip
\begin{tablenotes}
\item[a] some explanation
\item[b] this is why \dots
\item[c] see reference awesome
\item[d] hello world
\item
\end{tablenotes}
\end{threeparttable}
\end{document}

rowcolor command from colortbl package leaves unwanted gaps in shading between columns

2 Answers2