[Tex/LaTex] Histogram: different color for each bar

Question

I have the following code.

\documentclass[a4paper,twoside,12pt]{article}

\usepackage[T1]{fontenc}
\usepackage[utf8x]{inputenc}
\usepackage[english]{babel}
\usepackage{pgfplotstable}

\definecolor{color1}{rgb}{0.98, 0.81, 0.69}
\definecolor{color2}{rgb}{0.55, 0.71, 0.0}
\definecolor{color3}{rgb}{1.0, 0.6, 0.4}
\definecolor{color4}{rgb}{0.29, 0.59, 0.82}

\pgfplotscreateplotcyclelist{mycolor}{
{fill=color1!80, draw=color1},
{fill=color2!80, draw=color2},
{fill=color3!80, draw=color3},
{fill=color4!80, draw=color4},
}

\begin{filecontents*}{coefficienti.dat}
T       K       Q       Kf      n
400     0.0463  32.9        5.78        0.321
500     0.124   24.8        6.30        0.275
600     0.115   24.6        6.30        0.261
700     1.64        24.4        11.9        0.151
\end{filecontents*}

\begin{document}

\begin{tikzpicture}
    \begin{axis} [
        ymin=0,
        ybar=0, bar width=20, bar shift=0,
        xtick={1,2,3,4},
        xticklabels from table={coefficienti.dat}{T},
        ymajorgrids=true,
        cycle list name=mycolor,
        nodes near coords,
        every node near coord/.append style = {
            /pgf/number format/.cd,
            fixed,
            fixed zerofill,
            precision=3
        }]
        \addplot table [x=T,y=K] {coefficienti.dat};
    \end{axis}
\end{tikzpicture}

\end{document}

The result is the following graph (don't care about the color, I know it's horrible).

1. I would like that each bar has a different color from the list mycolor. How can I do?

2. In the x axis I would like to put the values of the column T of the table coefficienti.dat. How can I do?

Answer 1

Here's one option using a loop and a filter (the discard if not style defined in Jake's answer to Different color for individual bar in bar chart & adding bar labels);

Since xtick=data places labels for the data on the first plot only, the first plot is left out of the loop to get all the labels:

\documentclass[a4paper,twoside,12pt]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8x]{inputenc}
\usepackage[english]{babel}
\usepackage{pgfplotstable}

\definecolor{color1}{rgb}{0.98, 0.81, 0.69}
\definecolor{color2}{rgb}{0.55, 0.71, 0.0}
\definecolor{color3}{rgb}{1.0, 0.6, 0.4}
\definecolor{color4}{rgb}{0.29, 0.59, 0.82}

\pgfplotscreateplotcyclelist{mycolor}{
{fill=color1!80, draw=color1},
{fill=color2!80, draw=color2},
{fill=color3!80, draw=color3},
{fill=color4!80, draw=color4},
}

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


\begin{filecontents*}{coefficienti.dat}
T       K       Q       Kf      n
400     0.0463  32.9        5.78        0.321
500     0.124   24.8        6.30        0.275
600     0.115   24.6        6.30        0.261
700     1.64        24.4        11.9        0.151
\end{filecontents*}

\begin{document}

\begin{tikzpicture}
    \begin{axis} [
        ymin=0,
        ybar=0, bar width=20, bar shift=0,
        xtick={data},
        ymajorgrids=true,
        cycle list name=mycolor,
        nodes near coords,
        every node near coord/.append style = {
            /pgf/number format/.cd,
            fixed,
            fixed zerofill,
            precision=3
        }]

% first complete plot to place the x-axis labels
\addplot+ table[x=T,y=K] {coefficienti.dat};
% the bars with different colors
\pgfplotsinvokeforeach{500,600,700}{        
  \addplot+[discard if not={T}{#1}] table[x=T,y=K] {coefficienti.dat};
}
\end{axis}
\end{tikzpicture}

\end{document}