Is it possible to change the color of a single bar when the bar plot is based on symbolic values?

Question

I am beginner in LaTeX, trying to use it for industrial documents. I wonder if there is a way to change the color of only one bar of the plot below, ie "TestDetails", to illustrate it is a local macro and not a LaTeX keyword. I have been trying to experiment with point meta, but could not find a way.

\documentclass{article}
\usepackage{filecontents} 
\usepackage{pgfplots} 
\usepackage{pgfplotstable}
\pgfplotsset{width=.95\textwidth, compat=newest} 

\begin{document}

\begin{filecontents}{data.csv}
{Occurences}, {keyword}
215, item
159, SI
134, subsubsection
106, TestDetails
58, caption
\end{filecontents}

\pgfplotstableread[col sep=comma]{data.csv}{\datatable}

\begin{tikzpicture}
\begin{axis}[
/pgf/number format/.cd,1000 sep={},
width=0.8\linewidth,height=6cm,
xbar,
xmin=30, xmax=250,
xtick=\empty,
enlarge x limits={value=0.1, upper},
enlarge y limits=0.1,
ytick=data, 
y dir=reverse,
xlabel= {},
y tick label style={major tick length=0pt},
yticklabels from table={\datatable}{[index]1},
nodes near coords, nodes near coords align=horizontal,
]
\addplot [draw,fill=blue!50]table[
y expr=\coordindex,
x index=0]{\datatable};
\end{axis}
\end{tikzpicture}

\end{document}

Answer 1

You can't change the colour of an individual bar as such, but you can add a second \addplot where you filter out all bars but the one you want to highlight.

Here are two styles discard if and discard if not, which take two arguments: The name of the column in your table and the value that you want to highlight. Note that you'll need to supply the datafile itself to the \addplot, it doesn't work with a table created using \pgfplotstableread, and that you'll need to use xtick={<list>} instead of xtick=data, as otherwise your labels will be out of sync.

\documentclass{standalone}
\usepackage{filecontents} 
\usepackage{pgfplots} 
\usepackage{pgfplotstable}
\pgfplotsset{width=.95\textwidth, compat=newest} 

\pgfplotsset{
    discard if/.style 2 args={
        x filter/.code={
            \edef\tempa{\thisrow{#1}}
            \edef\tempb{#2}
            \ifx\tempa\tempb
                \def\pgfmathresult{inf}
            \fi
        }
    },
    discard if not/.style 2 args={
        x filter/.code={
            \edef\tempa{\thisrow{#1}}
            \edef\tempb{#2}
            \ifx\tempa\tempb
            \else
                \def\pgfmathresult{inf}
            \fi
        }
    }
}

\begin{document}

\begin{filecontents}{data.csv}
{Occurences}, {keyword}
215, item
159, SI
134, subsubsection
106, TestDetails
58, caption
\end{filecontents}

\pgfplotstablegetrowsof{data.csv}
\edef\numberofrows{\pgfplotsretval}

\begin{tikzpicture}
\begin{axis}[
/pgf/number format/.cd,1000 sep={},
width=0.8\linewidth,height=6cm,
xbar,/pgf/bar shift=0pt,
xmin=0, xmax=250,
xtick=\empty,
enlarge x limits={value=0.1, upper},
enlarge y limits=0.1,
ytick={0,...,\numberofrows}, 
y dir=reverse,
xlabel= {},
y tick label style={major tick length=0pt},
yticklabels from table={data.csv}{[index]1},
nodes near coords, nodes near coords align=horizontal
]

\addplot [draw,fill=blue!50,discard if={keyword}{TestDetails}
] table [
    y expr=\coordindex,
    x index=0,col sep=comma
]{data.csv};

\addplot [draw,fill=orange,discard if not={keyword}{TestDetails}] table [
    y expr=\coordindex,
    x index=0,col sep=comma
]{data.csv};
\end{axis}
\end{tikzpicture}

\end{document}