Draw two circles with line connecting them as in attachment

Question

Would you please help me in drawing two circles with a line (middle arrow) connecting them.

O-->--O

Sorry I could not post the image.

Edit* Thank you so much.

Can you help me more? Here is my code. I need to draw that mid-arrowed line between the dot-filled circles.

Thank you

\begin{tikzpicture}
\draw [dotted] (0,1) -- (0,10);
\draw [dotted] (1.5,1.3) -- (1.5,10);
\draw [dotted] (3.0,1.3) -- (3.0,10);
\draw [dotted] (4.5,1.3) -- (4.5,10);
\draw [dotted] (6.0,1.3) -- (6.0,10);
\draw [dotted] (7.5,1.3) -- (7.5,10);

% Lower Row
\filldraw[pattern=dots] (7.5,1) circle (0.2) ;
\filldraw[pattern=dots] (6.0,1) circle (0.2);
\filldraw[pattern=dots] (4.5,1) circle (0.2);
\draw (3.0,1) circle (0.2);
\end{tikzpicture}

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Can you post a link to an image showing what you need? A user with sufficient privileges will edit your question and insert it then. Plus it would be nice to post your code so far. — Count Zero, Dec 18 '12 at 11:15
Does TikZ: How to draw an arrow in the middle of the line? or TikZ-pgf directed graph: change arrow color and location help you in finding a solution for the arrow? How are the circles specified? The arrows library gives you o-o. — Qrrbrbirlbel, Dec 18 '12 at 11:36

score 7 · Answer 1 · answered Dec 18 '12 at 11:26

7

Something like this?

\input tikz
\usetikzlibrary{decorations.markings}
\tikzset{circ/.style={circle, draw, fill=white},
  conn/.style={postaction=decorate, decoration={
    markings, mark=at position .55 with {\arrow{stealth}}}}}

\tikz\draw[conn] (0,0) node[circ]{} -- +(1,0) node[circ]{};
\bye

enter image description here

answered Dec 18 '12 at 11:26

morbusg

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the description in the question sounds to me like a dynkin diagram. if that's the case, the circles here are much larger than the usual in such diagrams, and/or the arrowhead much smaller. – barbara beeton Dec 18 '12 at 14:05
@barbara: Yes, then it is more difficult (not the size of the circles; that could just be a, say, inner sep=.75ex, but all the other dynkin diagram reqs, like double lines with large angle arrows etc.) – morbusg Dec 20 '12 at 06:50

score 3 · Accepted Answer · answered Dec 18 '12 at 15:06

Here is a modification of your posted code with the arrows added.

Sample output

\documentclass{article}

\usepackage{tikz}
\usetikzlibrary{patterns,calc}

\begin{document}
\begin{tikzpicture}
  \draw [dotted] (0,1) -- (0,10);
  \draw [dotted] (1.5,1.3) -- (1.5,10);
  \draw [dotted] (3.0,1.3) -- (3.0,10);
  \draw [dotted] (4.5,1.3) -- (4.5,10);
  \draw [dotted] (6.0,1.3) -- (6.0,10);
  \draw [dotted] (7.5,1.3) -- (7.5,10);

  % Lower Row
  \draw[pattern=dots] (7.5,1) node[circle,minimum size=0.4cm,draw,fill] (A) {};
  \draw[pattern=dots] (6.0,1) node[circle,minimum size=0.4cm,draw,fill] (B) {};
  \draw[pattern=dots] (4.5,1) node[circle,minimum size=0.4cm,draw,fill] (C) {};
  \draw (3.0,1) circle (0.2);

  % Arrows
  \draw[->] (B.east) -- ($(B.east)!0.5!(A.west)$);
  \draw ($(B.east)!0.5!(A.west)$) -- (A.west);
  \draw[->] (C.east) -- ($(C.east)!0.5!(B.west)$);
  \draw ($(C.east)!0.5!(B.west)$) -- (B.west);
\end{tikzpicture}

\end{document}

The main change is to turn the circles in to nodes that are labelled. We can then refer to anchor positions such as A.west for attaching the lines.

Draw two circles with line connecting them as in attachment

2 Answers2