[Tex/LaTex] Customizing legend in pgfplots

pgfplotstikz-pgf

I am trying to customize the legend for this graph. First of all, I would like the legend width to be equal to the x-axis width. At the moment, I am setting the width of the legend via

 /tikz/every even column/.append style={column sep=1.0cm}

and I could manually adjust this value so that length equals the x-axis width, but I guess that there is a more elegant way to set the width of the legend.

Second, I don't really like the little color rectangles in the legend. I only want one rectangle in front of every entry and not two. This rectangle does not need to have a border and should be vertically centred with the text. The alignment seems to be okay for the rectangle closer to the text, but not for one the far left.

Update: Thanks to Christian Feuersänger's comment, there is possibility to change the rectangles via

legend image code/.code={%
    \draw[#1, draw=none] (0cm,-0.1cm) rectangle (0.6cm,0.1cm);

or what Gonzalo Medina proposed

legend image code/.code={%
    \draw[#1, draw=none, /tikz/.cd, bar width=3pt, yshift=-0.2em, bar shift=0pt] %
    plot coordinates {(2*\pgfplotbarwidth,0.6em)};

Third, I would like to the legend entries to start next to the text "Legend:".

I don't really know if with these requirements it still makes sense to use legend or if it would be better to add everything manually via after end axis/.code and \ref{label}.

Graph

enter image description here

MWE

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}

\begin{document}
\begin{tikzpicture}
    \begin{axis}[
                ybar,
                height=6cm,
                title={Some plot},
                width=12cm,
                axis on top,
                y axis line style={opacity=0},
                axis x line*=bottom,
                tick align=inside,
                tick style={draw=none},
                xtick=data,
                ymajorgrids,
                major grid style={draw=white},
                xtick={1,2,3,4},
                legend style={
                    at={(0.0,-0.15)},
                    anchor=north west,
                    legend columns=-1,
                    /tikz/every even column/.append style={column sep=1.0cm}
                        },
            ]       
            \addlegendimage{empty legend}
            \addlegendentry{\textbf{Legend:}}                   
            \addplot coordinates {
                (1, 0.2064)
                (2, 0.3961)
                (3, 0.5961)
                (4, 0.7961)}; \addlegendentry[text width=45pt, text depth=]{legend a}
            \addplot coordinates {
                (1, 0.3064)
                (2, 0.4961)
                (3, 0.6961)
                (4, 0.8961)}; \addlegendentry[text width=65pt, text depth=]{lengend b}
    \end{axis} 
\end{tikzpicture}
\end{document}

Best Answer

Regarding your first question:

How can I configure the legend such that it occupies a prescribed amount of space like the width of the figure?

To my knowledge, this is impossible by means of a PGF \matrix -- and these kind of legends are a PGF \matrix. As considered in your question, the remaining option would be to \label every plot and generate a legend manually using \ref to each plot, for example using

enter image description here

\documentclass{standalone}

\usepackage{pgfplots}
\pgfplotsset{compat=newest}

\begin{document}
\begin{tikzpicture}
    \def\INNERSEP{2pt}
    \def\WIDTH{12cm}
    \begin{axis}[
                ybar,
                height=6cm,
                title={Some plot},
                width=\WIDTH,
                scale only axis, % <------------
                axis on top,
                y axis line style={opacity=0},
                axis x line*=bottom,
                tick align=inside,
                tick style={draw=none},
                xtick=data,
                ymajorgrids,
                major grid style={draw=white},
                xtick={1,2,3,4},
                legend image code/.code={%
                    \draw[#1, draw=none] (0cm,-0.1cm) rectangle (0.6cm,0.1cm);
                },  
                extra description/.code={
                    \node[
                        draw,
                        text depth=0pt,
                        at={(0.0,-0.15)},
                        anchor=north west,
                        text width=\WIDTH-2*\INNERSEP,
                        inner sep=\INNERSEP,
                        outer sep=0pt,
                    ] {
                        % Some TeX/LaTeX construct which constructs
                        % the legend:
                        \hbox to \linewidth{%
                            \textbf{Legend:} 
                            \ref{A} Legend a \hfill \ref{B} Legend b \hfill
                        }%
                    };
                },
            ]       
            \addplot coordinates {
                (1, 0.2064)
                (2, 0.3961)
                (3, 0.5961)
                (4, 0.7961)};
                \label{A}
            \addplot coordinates {
                (1, 0.3064)
                (2, 0.4961)
                (3, 0.6961)
                (4, 0.8961)};
                \label{B}
    \end{axis} 
\end{tikzpicture}
\end{document}

Regarding your second question:

How can I recondigure the appearance of the small images for each plot?

As pointed out in some comment, the small images shown in legends can be reconfigured using legend image code. A suitable substitute for the small bars might be to use some rectangles (as in your edit).

enter image description here

\documentclass{standalone}

\usepackage{pgfplots}
\pgfplotsset{compat=newest}

\begin{document}
\begin{tikzpicture}
    \begin{axis}[
                ybar,
                height=6cm,
                title={Some plot},
                width=12cm,
                axis on top,
                y axis line style={opacity=0},
                axis x line*=bottom,
                tick align=inside,
                tick style={draw=none},
                xtick=data,
                ymajorgrids,
                major grid style={draw=white},
                xtick={1,2,3,4},
                legend image code/.code={%
                    \draw[#1, draw=none] (0cm,-0.1cm) rectangle (0.6cm,0.1cm);
                },  
                legend style={
                    draw=none, % ?
                    text depth=0pt,
                    at={(0.0,-0.15)},
                    anchor=north west,
                    legend columns=-1,
                    % default spacing:
                    column sep=1cm,
                    % The text "Legend:"
                    /tikz/column 2/.style={column sep=0pt,font=\bfseries},
                    %
                    % the space between legend image and text:
                    /tikz/every odd column/.append style={column sep=0cm},
                },
            ]       
            \addlegendimage{empty legend}
            \addlegendentry{\textbf{Legend:}}                   
            \addplot coordinates {
                (1, 0.2064)
                (2, 0.3961)
                (3, 0.5961)
                (4, 0.7961)}; \addlegendentry{legend a}
            \addplot coordinates {
                (1, 0.3064)
                (2, 0.4961)
                (3, 0.6961)
                (4, 0.8961)}; \addlegendentry{lengend b}
    \end{axis} 
\end{tikzpicture}
\end{document}

Regarding the third question:

How can I reconfigure the legend such that it starts right next to the text 'Legend:'?

You can distribute the column sep such that it does not apply to your first artificial legend entry if you configure /tikz/column 2/.style. I did that in the example above.

You will note that I also added draw=none due to the lacking support for your first question.

Related Solutions

[Tex/LaTex] plotting two time series with bounds

This happens because PGFPlots only uses one "stack" per axis: You're stacking the second confidence interval on top of the first. The easiest way to fix this is probably to use the approach described in "Is there an easy way of using line thickness as error indicator in a plot?": After plotting the first confidence interval, stack the upper bound on top again, using stack dir=minus. That way, the stack will be reset to zero, and you can draw the second confidence interval in the same fashion as the first:

\documentclass{standalone}
\usepackage{pgfplots, tikz}

\usepackage{pgfplotstable}

\pgfplotstableread{
temps   y_h y_h__inf    y_h__sup    y_f y_f__inf    y_f__sup    

1   0.237340    0.135170    0.339511    0.237653    0.135482    0.339823    
2   0.561320    0.422007    0.700633    0.165871    0.026558    0.305184    
3   0.694760    0.534205    0.855314    0.074856    -0.085698   0.235411    
4   0.728306    0.560179    0.896432    0.003361    -0.164765   0.171487    
5   0.711710    0.544944    0.878477    -0.044582   -0.211349   0.122184    
6   0.671241    0.511191    0.831291    -0.073347   -0.233397   0.086703    
7   0.621177    0.471219    0.771135    -0.088418   -0.238376   0.061540    
8   0.569354    0.431826    0.706882    -0.094382   -0.231910   0.043146    
9   0.519973    0.396571    0.643376    -0.094619   -0.218022   0.028783    
10  0.475121    0.366990    0.583251    -0.091467   -0.199598   0.016664    
}{\table}

\begin{document}
\begin{tikzpicture}

    \begin{axis}
    % y_h confidence interval
    \addplot [stack plots=y, fill=none, draw=none, forget plot]   table [x=temps, y=y_h__inf]   {\table} \closedcycle;
    \addplot [stack plots=y, fill=gray!50, opacity=0.4, draw opacity=0, area legend]   table [x=temps, y expr=\thisrow{y_h__sup}-\thisrow{y_h__inf}]   {\table} \closedcycle;
    % subtract the upper bound so our stack is back at zero
    \addplot [stack plots=y, stack dir=minus, forget plot, draw=none] table [x=temps, y=y_h__sup] {\table};

    % y_f confidence interval
    \addplot [stack plots=y, fill=none, draw=none, forget plot]   table [x=temps, y=y_f__inf]   {\table} \closedcycle;
    \addplot [stack plots=y, fill=gray!50, opacity=0.4, draw opacity=0, area legend]   table [x=temps, y expr=\thisrow{y_f__sup}-\thisrow{y_f__inf}]   {\table} \closedcycle;

    % the line plots (y_h and y_f)    
    \addplot [stack plots=false, very thick,smooth,blue]  table [x=temps, y=y_h]   {\table};
    \addplot [stack plots=false, very thick,smooth,blue]  table [x=temps, y=y_f]   {\table};
    \end{axis}

\end{tikzpicture}
\end{document}

[Tex/LaTex] How to increase legend lines lengths in PGFplots

A sample:

\documentclass{article}
\usepackage{pgfplots}
\begin{document}
\pgfplotsset{
    compat=newest,
    /pgfplots/legend image code/.code={%
        \draw[mark repeat=2,mark phase=2,#1] 
            plot coordinates {
                (0cm,0cm) 
                (0.3cm,0cm)
                (0.6cm,0cm)
                (0.9cm,0cm)
                (1.2cm,0cm)%
            };
    },
}
\begin{tikzpicture}
    \begin{axis}
        \addplot+[dashdotted,mark=triangle] plot {x^2};
        \addlegendentry{a}
        \addplot+[dotted,mark=*] plot {1};
        \addlegendentry{b}
        \addplot+[mark=star] plot {x};
        \addlegendentry{c}
    \end{axis}
\end{tikzpicture}
\end{document}

Another sample

    plot coordinates {
        (0cm,0cm) 
        (0.3cm,.1cm)
        (0.6cm,0cm)
        (0.9cm,-.1cm)
        (1.2cm,0cm)%
    };

Explanation

Go to pgfplots.code.tex and find this:

/pgfplots/line legend/.style={%
  /pgfplots/legend image code/.code={%
      \draw[mark repeat=2,mark phase=2,##1] 
          plot coordinates {
              (0cm,0cm) 
              (0.3cm,0cm)
              (0.6cm,0cm)%
          };%
  }%
},    
/pgfplots/line legend/.style/.code={\pgfplots@error{This style is supposed to be constant.}},%
/pgfplots/line legend/.append style/.code={\pgfplots@error{This style is supposed to be constant.}},%

This shows us that

A legend entry is indeed a plot;
that plot consists of three fixed point, the second marked; and last, but the worst
you cannot modify this style anymore because /.style/.code make it meaningless to say /.style={new style}. (It throw the error and ignore your suggestion)

So... in general, one solution is to copy pgfplots.code.tex to your current folder and modify those lines to, say,

    /pgfplots/line legend/.style={%
        /pgfplots/legend image code/.code={%
            \draw[mark repeat=2,mark phase=2,##1] 
                plot coordinates {
                    (0cm,0cm) 
                    (0.3cm,0cm)
                    (0.6cm,0cm)
                    (0.9cm,0cm) 
                    (1.2cm,0cm)%
                };%
        }%
    },

But at the beginning of my answer I need no new pgfplots.code.tex because we do not really care about /pgfplots/line legend/.style and we can simply manipulate /pgfplots/legend image code/.code. However, one obvious drawback is that it nullifies any previous /pgfplots/legend image code/.add code, or .append code or .prefix code.

About distance of marks

In your case, the default samples=25 and domain=-5:5 are used. So there is one mark every .4 unit in x direction. Therefore we expect the following assignment gives the correct result.

        plot coordinates {
            (axis cs:.0,-5)
            (axis cs:.2,-5)
            (axis cs:.4,-5)
            (axis cs:.6,-5)
            (axis cs:.8,-5)
        };

In general it is quite hard to tell the actual (horizontal) distance between marks since PgfPlots does scaling quite often. By general I meant that you may have data points with periodic x-values but periods vary from line to line. Manual calculation is doable only if you are plotting a function. But then (a) you do not need PgfPlots but TikZ and (b) it is meaningless to add marks which represent data.

Graph

MWE

Best Answer

Related Solutions

[Tex/LaTex] plotting two time series with bounds

[Tex/LaTex] How to increase legend lines lengths in PGFplots

Explanation

About distance of marks

Related Question