Align bar graph with error bars in groups on Y-axis

Question

Am trying to align this in group of 3's but a bar in the AAAAAAAA group keeps going off alignment.

Note: I have checked "grouped bar chart with pgfplots" , "Bar graph with groups(inner group bars next to each other) and whitespace between groups including error bars [duplicate]" and "How can i create bar plot groups of different sizes in pgfplots?" and they don't answer my question - our data input format is different.

MWE:

\definecolor{bblue}{HTML}{82B1FF}
\definecolor{rred}{HTML}{FF8A80}

\begin{filecontents}{testdata.csv}
ALB,VAL,ERR,COR
AA,20.61,0.32,bblue
AA,20.88,0.55,bblue
AA,20.41,0.29,bblue
AAA,26.22,0.94,bblue
AAA,26.43,0.45,bblue
AAA,26.86,0.61,bblue
AAAA,29.91,0.76,bblue
AAAA,30.39,0.11,bblue
AAAA,30.11,0.49,bblue
AAAAA,34.71,0.43,rred
AAAAA,34.87,0.99,rred
AAAAA,34.81,0.26,rred
AAAAAA,40.33,0.64,rred
AAAAAA,40.18,0.03,rred
AAAAAA,40.4,0.83,rred
AAAAAAA,45.77,0.47,rred
AAAAAAA,45.93,0.95,rred
AAAAAAA,45.35,0.3,rred
AAAAAAAA,50.35,0.13,rred
AAAAAAAA,50.34,0.85,rred
AAAAAAAA,50.66,0.55,rred
\end{filecontents}
\pgfplotstableread[col sep=comma]{testdata.csv}\datatable
\makeatletter
\pgfplotsset{
    /pgfplots/flexible yticklabels from table/.code n args={3}{%
        \pgfplotstableread[#3]{#1}\coordinate@table
        \pgfplotstablegetcolumn{#2}\of{\coordinate@table}\to\pgfplots@yticklabels
        \let\pgfplots@yticklabel=\pgfplots@user@ticklabel@list@y
    }
}
\makeatother
\begin{figure}

\begin{tikzpicture}
\begin{axis}[
    ylabel=A labels,  y label style={at={(-0.1,0.5)}}, 
    y = -0.3cm,
    ybar, %=2*\pgflinewidth,
    draw opacity=0.5,
    bar width=6pt,
    enlarge y limits={abs=7pt},
    xbar, 
    width=.36\textwidth,
    xlabel= unit,
    %flexible xticklabels from table={testdata.csv}{ALB}{col sep=comma}, 
    flexible yticklabels from table={testdata.csv}{ALB}{col sep=comma},
    yticklabel style={font=\small,xshift=0.5ex,  anchor=east},  
    %xtick=data
    ytick=data,
    xmajorgrids
]
%\pgfplotsinvokeforeach {0}{
    \addplot
    %style={color=cyan,fill=bblue,mark=none};
    plot [error bars/.cd, x dir=both,x explicit ] 
        table[y expr={(\coordindex) - mod(\coordindex,3)/8},x=VAL, x error=ERR ] {\datatable};

\end{axis}

\end{tikzpicture} 
\end{figure}

Answer 1

(Update 21.10.17.) This problem was caused by a bug in the floating point library: https://sourceforge.net/p/pgfplots/bugs/187/ It has been fixed by Christian Feuersänger, and when the next version of pgf or pgfplots is released the code should work properly without the workaround described below.

---

It could be that the 18 is seen as 17.99999 or something, so the mod gives the wrong output.

If you change to mod(\coordindex+0.001,3) the output is as expected.

Unrelated comments:

• you have both ybar and xbar in the axis options, the ybar can be removed.
• \addplot plot[.. is mixing TikZ syntax (\draw plot) with pgfplots syntax, you want \addplot +[.. I think.
• As shown, you don't really need the flexible yticklabels stuff, yticklabels from table={\datatable}{ALB} is good enough.

\documentclass{article}
\usepackage{pgfplotstable,filecontents}

\begin{document}

\definecolor{bblue}{HTML}{82B1FF}
\definecolor{rred}{HTML}{FF8A80}

\begin{filecontents}{testdata.csv}
ALB,VAL,ERR,COR
AA,20.61,0.32,bblue
AA,20.88,0.55,bblue
AA,20.41,0.29,bblue
AAA,26.22,0.94,bblue
AAA,26.43,0.45,bblue
AAA,26.86,0.61,bblue
AAAA,29.91,0.76,bblue
AAAA,30.39,0.11,bblue
AAAA,30.11,0.49,bblue
AAAAA,34.71,0.43,rred
AAAAA,34.87,0.99,rred
AAAAA,34.81,0.26,rred
AAAAAA,40.33,0.64,rred
AAAAAA,40.18,0.03,rred
AAAAAA,40.4,0.83,rred
AAAAAAA,45.77,0.47,rred
AAAAAAA,45.93,0.95,rred
AAAAAAA,45.35,0.3,rred
AAAAAAAA,50.35,0.13,rred
AAAAAAAA,50.34,0.85,rred
AAAAAAAA,50.66,0.55,rred
\end{filecontents}
\pgfplotstableread[col sep=comma]{testdata.csv}\datatable

\begin{figure}

\begin{tikzpicture}
\begin{axis}[
    ylabel=A labels,
    y label style={at={(-0.1,0.5)}}, 
    y = -0.3cm,
    xbar, %=2*\pgflinewidth,
    draw opacity=0.5,
    bar width=6pt,
    enlarge y limits={abs=7pt},
    width=.36\textwidth,
    xlabel= unit,
    yticklabels from table={\datatable}{ALB},
    yticklabel style={font=\small,xshift=0.5ex,  anchor=east},  
    ytick=data,
    xmajorgrids
]
%\pgfplotsinvokeforeach {0}{
    \addplot
    %style={color=cyan,fill=bblue,mark=none};
    +[error bars/.cd, x dir=both,x explicit] 
        table[y expr={(\coordindex) - mod(\coordindex+0.001,3)/8},x=VAL, x error=ERR ] {\datatable};

\end{axis}

\end{tikzpicture} 
\end{figure}
\end{document}