Plot and label data from file with PGFPlots

Question

Given some data from a file, I would like to use the first two columns as coordinates, and the second two columns as label for every point. The data is given in this form:

x                        y                        labela                   labelb
1.416197036356566059e+02 5.144315570548267715e+03 7.000000000000000000e+00 1.000000000000000000e+00

I use the table command to read the first two columns as data:

\begin{tikzpicture}
    \begin{axis}
        \addplot+[only marks,x=x, y=y, ] table {DataTable.dat};
    \end{axis}
\end{tikzpicture}

The data of the second column should appear above each scatter point as simple text or may be in a bubble like this: labela / labelb.

A promising option seems to be the option nodes near coords which I use to show the y-coordinate of points in other plots, but I don't see how I can use the data from the file and combine it with that.

Answer 1

nodes near coords is the right approach. You can make your two label columns available inside the label nodes using the key visualization depends on=\thisrow{<column name>} \as \<macro name>. The key can be called as often as you like.

Then, you can typeset the labels using nodes near coords=\pgfmathprintnumber{\<macronameA>} / \pgfmathprintnumber{\<macronameB>}. The styles for the label nodes can be set using every node near coord/.append style=<styles>.

Note that the label nodes will not automatically increase the axis limits, so they might overlap the axes. In that case, you'll need to use enlargelimits or enlarge y limits.

\documentclass{article}

\usepackage{pgfplots}

\begin{filecontents}{DataTable.dat}
x                        y                        labela                   labelb
1.416197036356566059e+02 5.144315570548267715e+03 7.000000000000000000e+00 1.000000000000000000e+00
2.416197036356566059e+02 3.144315570548267715e+03 8.000000000000000000e+00 4.000000000000000000e+00
4.416197036356566059e+02 1.144315570548267715e+03 6.000000000000000000e+00 2.000000000000000000e+00
\end{filecontents}
\begin{document}
\begin{tikzpicture}
    \begin{axis}[enlarge y limits={upper,value=0.3}]
        \addplot+[
            only marks,
            visualization depends on=\thisrow{labela} \as \labela,
            visualization depends on=\thisrow{labelb} \as \labelb,
            nodes near coords=\pgfmathprintnumber{\labela}/\pgfmathprintnumber{\labelb},
            every node near coord/.append style={
                black,
                draw,
                circle,
                inner sep=1pt,
                yshift=1ex
            }
            ] table {DataTable.dat};
    \end{axis}
\end{tikzpicture}

\end{document}