Plotting a directed graph using pgfplots

Question

I have a few files in the following format:

x   y
12  12
12  13
13  15
15  15
15  13
13  12
12  10
10  8
8   8
8   10
10  12
12  12
12  10
10  10

And I wanted to plot them as a directed graph in a .tex file using pgfplots.

The code I am currently using is this one

\usepackage{pgfplots}

\begin{center}
\begin{tikzpicture}
\begin{axis}[title=File1,
             xlabel={},
             ylabel={}]
\addplot table {data-1.txt};
\end{axis}
\end{tikzpicture}
\end{center}

This plots the points with lines between them but it is not enough for what I need. I would like to

1. Set a different color for the first point
2. Have arrows indicating between the dots indicating the "path" the dots take.

Some files (as the one in the example) may have overlapping nodes. If your solution could handle this scenario it would save me a lot of effort.

Another thing that I would like to do would be to do a linear interpolation of the points in the D-Graph that is generated. However I am totally clueless about how I am going to do that. I know that this seems rather awkward and might even be impossible with the most common linear interpolation algorithms, but if you could lend me a hand in that I would be very grateful.

As an example of the process described above, I would like to get something similar to this:

Answer 1

A solution with PSTricks. It needs http://texnik.dante.de/tex/generic/pst-node/pst-node.tex Run it with xelatex:

\documentclass[a4paper]{article}
\usepackage{filecontents}
\begin{filecontents*}{node.data}
12  12
12  13
13  15
15  15
15  13
13  12
12  10
10  8
8   8
8   10
\end{filecontents*}

\usepackage{pst-node,pst-plot}

\begin{document}
\begin{pspicture}(6.5,6.5)(16,16)
  \psaxes[axesstyle=frame,ticksize=0 9cm,tickcolor=black!20,Ox=7,Oy=7](7,7)(16,16)
  \saveDataAsNodes{node.data}{N}
  \psset{radius=2.5mm,arrows=->,arrowscale=1.5,nodesep=2.7mm,linewidth=1.3pt}
  \Cnodeput[linecolor=red]{0}(N0){foo}{0}
  \multido{\iA=1+1,\iB=0+1}{\numexpr\the\psLoopIndex-1}{%
    \Cnodeput{0}(N\iA){foo}{\iA}\ncline{N\iB}{N\iA}}
  \readdata\data{node.data}
  \listplot[plotstyle=LSM,linestyle=dashed,linecolor=blue,xStart=7,xEnd=16]{\data}
\end{pspicture}

\end{document}

The equation of the linear regression line can be plotted with \PstDebug=1:

The nodes are named N0... N9. Any connection with any offset between the nodes is possible.

A solution for multiple nodes which are overwritten, only the last one is printed:

\documentclass[a4paper]{article}
\usepackage{filecontents}
\begin{filecontents*}{node2.data}
12  12
12  13
13  15
15  15
15  13
13  12
12  10
10  8
8   8
8   10
10  12
12  12
12  10
10  10
\end{filecontents*}
\usepackage{pst-node,pst-plot}
\def\CPut(#1)#2{\pscircle*[linecolor=white](#1){3mm}\rput(#1){#2}\pscircle(#1){3mm}}

\begin{document}
\begin{pspicture}(6.5,6.5)(16,16)
  \psaxes[axesstyle=frame,ticksize=0 9cm,tickcolor=black!20,Ox=7,Oy=7](7,7)(16,16)
  \saveDataAsNodes{node2.data}{N}
  \psset{radius=2.5mm,arrows=->,arrowscale=1.5,nodesep=3mm,linewidth=1.3pt}
  \multido{\iA=\the\psLoopIndex+-1,\iB=\numexpr\the\psLoopIndex-1\relax+-1}%
     {\the\psLoopIndex}{\CPut(N\iA){\iA}\ncline{N\iB}{N\iA}}
  \pscircle*[linecolor=red](N0){3mm}\rput(N0){\bf\white0}
  \readdata\data{node2.data}
  \pslistplot[linecolor=blue,linestyle=dashed,plotstyle=LSM,xStart=7,xEnd=16]{\data}
\end{pspicture}
\end{document}

If you need some information on the connection itself use (\ncput):

  \multido{\iA=\the\psLoopIndex+-1,\iB=\numexpr\the\psLoopIndex-1\relax+-1}%
     {\the\psLoopIndex}{\CPut(N\iA){\iA}\ncline{N\iB}{N\iA}\ncput*[npos=0.4]{\tiny\iB/\iA}}

Answer 2

Here's an approach that uses the code from Gap between line and point in pgfplots, like pointintervalbox in gnuplot to draw arrows between the coordinates.

\documentclass[border=5mm]{standalone}

\usepackage{pgfplots, pgfplotstable}
\makeatletter
\pgfplotsset{
    discontinuous line/.code={
        \pgfkeysalso{mesh, shorten <=#1, shorten >=#1}
        \def\pgfplotsplothandlermesh@VISUALIZE@std@fill@andor@stroke{%
            \pgfplotspatchclass{\pgfplotsplothandlermesh@patchclass}{fill path}%
            \pgfplotsplothandlermesh@definecolor
            \pgfusepath{stroke}
            \pgfplotsplothandlermesh@show@normals@if@configured
        }%
    },
    discontinuous line/.default=1.5mm
}
\makeatother

\begin{document}

\pgfplotstableread{
x   y
12  12
12  13
13  15
15  15
15  13
13  12
12  10
10  8
8   8
8   10
}\datatable

\begin{tikzpicture}
\begin{axis}[
    title=File1,
    width=10cm
]
\addplot [
    discontinuous line=2.5mm,
    very thick, black, -latex,
    nodes near coords=\coordindex,
    every  node near coord/.style={
        draw,
        circle,
        anchor=center,
        inner sep=1.5pt,
        color={\ifnum\coordindex=0 red\else black\fi}
    }] table {\datatable};

\addplot [ultra thick, blue] table [y={create col/linear regression={y=y}}] {\datatable};
\end{axis}
\end{tikzpicture}

\end{document}