6

Can someone help me to draw a horizontal parallel arrows as a co-equalizer diagram in tikz-cd?

An example of co-equalizer diagram is:

enter image description here

Thanks in advance!

  • 5
    Welcome to TeX.SX! On this site, a question should typically revolve around an abstract issue (e.g. "How do I get a double horizontal line in a table?") rather than a concrete application (e.g. "How do I make this table?"). Questions that look like "Please do this complicated thing for me" tend to get closed because they are either "off topic", "too broad", or "unclear". Please try to make your question clear and simple by giving a minimal working example (MWE): you'll stand a greater chance of getting help. – ChrisS Oct 16 '14 at 8:38
  • 2
    The phrase “coequalizer diagram” is perfectly clear to everybody who has started category theory. It's a specialized mathematical field, but not at all unclear; googling for “coequalizer diagram” reveals this image and also this Wikipedia page – egreg Oct 16 '14 at 10:38
7

You can go with tikz-cd:

\documentclass{article}
\usepackage{tikz-cd}

\begin{document}
\[
\begin{tikzcd}
X \ar[r,shift left=.75ex,"f"]
  \ar[r,shift right=.75ex,swap,"g"]
&
Y \ar[r,"q"] \ar[dr,swap,"q'"]
&
Q \ar[d,densely dotted]
\\
& & Q'
\end{tikzcd}
\]
\end{document}

enter image description here

4

Just for fun, a pstricks solution:

\documentclass[pdf]{article}
\usepackage{pst-node}

\begin{document}

\[ \psset{arrows=->, arrowinset=0.25, linewidth=0.6pt, dash=3pt 2pt, nodesep=3pt, labelsep=2pt, colsep=1.2cm, rowsep=1cm}
\begin{psmatrix}
  X & Y & Q \\%
   & &Q\smash{'}
%%%
 \ncline[offset = 0.6ex]{1,1}{1,2}\naput{f} \ncline[offset = -0.6ex]{1,1}{1,2}\nbput{g}
 \ncline{1,2}{1,3}\nbput{q} \ncline{1,2}{2,3}\nbput{q'}
 \ncline[linestyle=dashed]{1,3}{2,3}\nbput[npos=0.45]{u}
\end{psmatrix}
\]

\end{document} 

enter image description here

  • Thanks to all for advices and right answers! Sorry for late response I was away for a week. – Kaythi Oct 20 '14 at 6:28
  • @Kaythi If you are satisfied with the answers, you should accept one as such. Like this, this issue will get closed. If you are waiting for some other answer, you should clarify what you need. – LaRiFaRi Oct 20 '14 at 15:09

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