Hello Shaun,
Shaun Morgan wrote:
> A quick question: is it possible to read coordinates from a file and `pipe'
> them in a pgfplots command?.
> For example, if I want to define a set of nodes based on coordinates in a
> file. Assume the file is:
> x1 y1 name_node_1
> x2 y2 name_node_2
> ...
>
> so pgfplots would read one line at a time and define the corresponding node.
Yes, that is possible using the advanced scatter plot interface. The
idea is to
a) use the "scatter" key to activate scattered data processing,
b) configure the "scatter/@pre marker code" and "scatter/@post marker
code" keys.
Here is a related example:
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\documentclass[10pt]{article}
\usepackage{pgfplots}
\begin{document}
First solution: uses table input with a ``name'' column (as in your
request):
\begin{tikzpicture}
\begin{axis}
\addplot+[% the '+' maintains the default color (blue)
scatter,
%mark=*,
%only marks,
scatter src=explicit symbolic,% to avoid numerical processing
of the
"meta=name" column
scatter/@pre marker code/.code={%
% define the named coordinate. At this time,
% \pgfplotspointmeta contains the value of the "scatter
% src", which is provided using "meta=name" below
\coordinate (\pgfplotspointmeta) at (0pt,0pt);
},
scatter/@post marker code/.code={},
]
table[meta=name] {% meta=name means: use the "name" col as "point
meta"(="scatter src")
x y name
0 0 node1
1 1 node2
2 2 node3
};
\end{axis}
\draw (node2) circle (5pt);
\end{tikzpicture}
Automatically assign named nodes to each input coord using
\verb|\coordindex|:
\begin{tikzpicture}
\begin{axis}
\addplot+[
scatter,
%mark=*,
%only marks,
scatter/@pre marker code/.code={%
% just use \coordinate, no need to provide an extra
% column:
\coordinate (node_no_\coordindex) at (0pt,0pt);
},
scatter/@post marker code/.code={},
] table {
x y
0 0
1 1
2 2
};
\end{axis}
\draw (node_no_0) circle (5pt);
\end{tikzpicture}
\end{document}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
I think this is what you asked for (please correct me in case I
misunderstood it).
Details for the procedure can be found in the manual, section scatter plots.
Best regards
Christian
--
Christian Feuersaenger
Institut fuer Numerische Simulation
Rheinische Friedrich-Wilhelms Universitaet Bonn
Wegelerstrasse 6
D-53115 Bonn
Germany
Tel: +49 228 733430
URL: http://wissrech.ins.uni-bonn.de/people/feuersaenger.html
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