Example: Chains with labeled edges

Published 2011-12-31 | Author: Stefan Kottwitz

TikZ chains with labeled edges

The chains library is very useful for writing exact sequences. Yet there’s no feature for labeling the edges of a chain. Besides arrows, we might need to write symbols for maps over, under, or just next to it.

This example shows a way by modifying the join method of the chains library. Its original syntax is join=with<node> by <options>, here the syntax is changed to join={node[options] {label}}.

Furthermore, we define a style for the labels, so that all are in math mode and typeset in scriptstyle.

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Chains with labeled edges

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% TikZ chains with labeled edges
% Author: Stefan Kottwitz , http://texblog.net
\tikzset{join/.code=\tikzset{after node path={%
edge[every join]#1(\tikzchaincurrent)\fi}}}
\tikzset{>=stealth',every on chain/.append style={join},
         every join/.style={->}}
\tikzstyle{labeled}=[execute at begin node=$\scriptstyle,
   execute at end node=$]
  \matrix (m) [matrix of math nodes, row sep=3em, column sep=3em]
    { 0 & A  & B  & C  & 0 \\
      0 & A' & B' & C' & 0 \\ };
  { [start chain] \chainin (m-1-1);
    \chainin (m-1-2);
    { [start branch=A] \chainin (m-2-2)
        [join={node[right,labeled] {\eta_1}}];}
    \chainin (m-1-3) [join={node[above,labeled] {\varphi}}];
    { [start branch=B] \chainin (m-2-3)
        [join={node[right,labeled] {\eta_2}}];}
    \chainin (m-1-4) [join={node[above,labeled] {\psi}}];
    { [start branch=C] \chainin (m-2-4)
        [join={node[right,labeled] {\eta_3}}];}
    \chainin (m-1-5); }
  { [start chain] \chainin (m-2-1);
    \chainin (m-2-2);
    \chainin (m-2-3) [join={node[above,labeled] {\varphi'}}];
    \chainin (m-2-4) [join={node[above,labeled] {\psi'}}];
    \chainin (m-2-5); }


  • #1 Eunate, September 24, 2012 at 7:47 p.m.

    how could I get this type of schema but vertical instead of horizontal? thank you!!! Eunate

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