Select color of a bar plot from table value

Question

I'm trying to select the color of a stacked bar plot based on the value of a cell in the line.

\documentclass{article}
\usepackage{pgfplots, pgfplotstable}
\usepackage[utf8]{inputenc}

\begin{document}

\pgfplotstableread[col sep=comma]{
label,startyear,endyear,color  
Washington, 1789, 1797, black!50
Adams, 1797, 1801, red!30
Jefferson, 1801, 1809, green!50
Madison, 1801, 1809, green!50
}\loadedtable
% sort by startyear
\pgfplotstablesort[sort key=startyear]\sortedtable\loadedtable

\begin{tikzpicture}
\begin{axis}[
  xbar stacked,
  xmin=1785,
  bar width=0.2cm,
  axis lines=left,
  width=\textwidth, height=4cm,
  enlarge y limits={abs=0.5},
  ytick=\empty,
]

\addplot [draw=none, forget plot] table [col sep=comma,x=startyear, y expr=-\coordindex]{\sortedtable};
\addplot +[
   nodes near coords,
   nodes near coords align={anchor=west},
   point meta=explicit symbolic, every node near coord/.append style={black}] table[col sep=comma,x expr=\thisrow{endyear}-\thisrow{startyear}, y expr=-\coordindex,meta=label]{\sortedtable};
\end{axis}
\end{tikzpicture}
\end{document}

I have not however found a way to get each row to be filled with the selected color.

Answer 1

It is not too difficult to draw these bars in different colors. Instead of drawing bars this draws rectangles that of course look like bars. The definition of the corresponding plot marks is from here. (I do not understand why you need to sort the table.)

\documentclass{article}
\usepackage{pgfplots, pgfplotstable}
\pgfplotsset{compat=1.16}
\usetikzlibrary{calc}
\usepackage[utf8]{inputenc}
\pgfkeys{/pgf/shapes/xbar/height/.initial=10cm,/pgf/shapes/xbar/width/.initial=6pt}
\pgfdeclareplotmark{xbar}{%
    \pgfpathrectangle{\pgfpoint{0pt}{-.5*\pgfkeysvalueof{/pgf/shapes/xbar/width}}{0pt}}{%
    \pgfpoint{-\pgfkeysvalueof{/pgf/shapes/xbar/height}}{\pgfkeysvalueof{/pgf/shapes/xbar/width}}}
    \pgfusepath{stroke,fill}}
\begin{document}

\pgfplotstableread[col sep=comma]{
label,startyear,endyear,color  
Washington, 1789, 1797, black!50
Adams, 1797, 1801, red!30
Jefferson, 1801, 1809, green!50
Madison, 1801, 1809, green!50
}\loadedtable
% sort by startyear
\pgfplotstablesort[sort key=startyear]\sortedtable\loadedtable

\begin{tikzpicture}
\begin{axis}[xmin=1785,xmax=1810,height=4cm,
  /pgf/shapes/xbar/width=0.2cm,
  axis lines=left,
  width=\textwidth, 
  enlarge y limits={abs=0.5},
  ytick=\empty,
  scatter/@pre marker code/.code={
  \pgfplotstablegetelem{\coordindex}{color}\of{\sortedtable}
  \edef\mycolor{\pgfplotsretval}
  \pgfplotstablegetelem{\coordindex}{startyear}\of{\sortedtable}
  \edef\startyear{\pgfplotsretval}
  \pgfplotstablegetelem{\coordindex}{endyear}\of{\sortedtable}
  \edef\endyear{\pgfplotsretval}
  \pgfmathsetmacro{\myheight}{(\endyear-\startyear)*\xunit}
  \scope[fill=\mycolor,/pgf/shapes/xbar/height=\myheight pt]},
]

\addplot [xbar stacked,draw=none, forget plot] table [col sep=comma,x=startyear, y expr=-\coordindex]{\sortedtable};
\path let \p1=($(1786,0)-(1785,0)$)    in \pgfextra{\xdef\xunit{\x1}}; % measure x unit
\addplot[only marks,scatter,mark=xbar,
   nodes near coords*,
   nodes near coords align={anchor=west},
   point meta=explicit symbolic, every node near coord/.append style={black}] 
 table[col sep=comma,y expr=-\coordindex,x expr=\thisrow{endyear},meta=label]{\sortedtable};

\end{axis}
\end{tikzpicture}
\end{document}

Here is a way to add a legend.

\documentclass{article}
\usepackage{pgfplots, pgfplotstable}
\pgfplotsset{compat=1.16}
\usetikzlibrary{calc}
\usepackage[utf8]{inputenc}
\pgfkeys{/pgf/shapes/xbar/height/.initial=10cm,/pgf/shapes/xbar/width/.initial=6pt}
\pgfdeclareplotmark{xbar}{%
    \pgfpathrectangle{\pgfpoint{0pt}{-.5*\pgfkeysvalueof{/pgf/shapes/xbar/width}}{0pt}}{%
    \pgfpoint{-\pgfkeysvalueof{/pgf/shapes/xbar/height}}{\pgfkeysvalueof{/pgf/shapes/xbar/width}}}
    \pgfusepath{stroke,fill}}
\begin{document}

\pgfplotstableread[col sep=comma]{
label,startyear,endyear,color  
Washington, 1789, 1797, black!50
Adams, 1797, 1801, red!30
Jefferson, 1801, 1809, green!50
Madison, 1801, 1809, green!50
}\loadedtable
% sort by startyear
\pgfplotstablesort[sort key=startyear]\sortedtable\loadedtable

\begin{tikzpicture}
\begin{axis}[xmin=1785,xmax=1810,height=4cm,
  /pgf/shapes/xbar/width=0.2cm,
  axis lines=left,
  width=\textwidth, 
  enlarge y limits={abs=0.5},
  ytick=\empty,
  scatter/@pre marker code/.code={
  \pgfplotstablegetelem{\coordindex}{color}\of{\sortedtable}
  \edef\mycolor{\pgfplotsretval}
  \pgfplotstablegetelem{\coordindex}{startyear}\of{\sortedtable}
  \edef\startyear{\pgfplotsretval}
  \pgfplotstablegetelem{\coordindex}{endyear}\of{\sortedtable}
  \edef\endyear{\pgfplotsretval}
  \pgfmathsetmacro{\myheight}{(\endyear-\startyear)*\xunit}
  \scope[fill=\mycolor,/pgf/shapes/xbar/height=\myheight pt]},
  legend style={at={(1,1.5)}}
]

\addplot [xbar stacked,draw=none, forget plot] table [col sep=comma,x=startyear, y expr=-\coordindex]{\sortedtable};
\path let \p1=($(1786,0)-(1785,0)$)    in \pgfextra{\xdef\xunit{\x1}}; % measure x unit
\addplot[only marks,scatter,mark=xbar,
   nodes near coords*,forget plot,
   nodes near coords align={anchor=west},
   point meta=explicit symbolic, every node near coord/.append style={black}] 
 table[col sep=comma,y expr=-\coordindex,x expr=\thisrow{endyear},meta=label]{\sortedtable};
 \pgfplotstablegetrowsof{\sortedtable} 
 \pgfmathtruncatemacro{\NumRows}{\pgfplotsretval-1} 
 \pgfplotsinvokeforeach{0,...,\NumRows}{
  \pgfplotstablegetelem{#1}{color}\of{\sortedtable}
  \edef\mycolor{\pgfplotsretval}
  \pgfplotstablegetelem{#1}{label}\of{\sortedtable}
  \edef\mylabel{\pgfplotsretval}
  \edef\temp{\noexpand\addlegendimage{area legend,fill=\mycolor}
  \noexpand\addlegendentry{\mylabel}}
  \temp
 }
\end{axis}
\end{tikzpicture}
\end{document}