I want to draw a nice connecting homomorphism arrow

Question

\begin{tikzpicture}[scale=1.5]

\node (A) at (0,0) {$0$};
\node (B) at (1,0) {$H^0(G,P)$};
\node (C) at (2,0) {$H^0(G,M)$};
\node (D) at (3,0) {$H^0(G,N)$};
\node (E) at (1,-1) {$H^1(G,P)$};
\node (F) at (2,-1) {$H^1(G,M)$};
\node (G) at (3,-1) {$H^1(G,N)$};
\path[->,font=\scriptsize,>=angle 90]
(A) edge node[above]{} (B)
(B) edge node[above]{$\phi$} (C)
(C) edge node[above]{$\psi$} (D)
(D) edge node[above]{} (E)
(E) edge node[above]{} (F)
(F) edge node[above]{} (G);

\end{tikzpicture}

So I've got this that I want to try and draw a 'nice' connecting homomorphism which I'll try my best to describe: It starts from the end of the last element in the first row and ends at the beginning of the first element in the second row.

Maybe it's better to do it in tikzcd but I don't know how to do that either.

See http://tex.stackexchange.com/q/3892/15925 – Andrew Swann Jun 12 '14 at 10:55 — Andrew Swann, Jun 12 '14 at 10:55

egreg · Answer 1 · 2014-06-11T22:12:43.007

21

With tikz-cd it's a piece of cake:

\documentclass{article}

\usepackage{tikz-cd}

\begin{document}

\begin{tikzcd}[scale=1.5]
0 \arrow{r} &
H^0(G,P) \arrow{r}{\phi} &
H^0(G,M) \arrow{r}{\psi} &
H^0(G,N) \arrow{dll} \\
&
H^1(G,P) \arrow{r} &
H^1(G,M) \arrow{r} &
H^1(G,N)
\end{tikzcd}

\end{document}

enter image description here

With a modification of the example in the documentation at the end of page 11 we can get a bent arrow:

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

\begin{document}

\begin{tikzcd}           
0 \arrow{r} &
H^0(G,P) \arrow{r}{\phi} &
H^0(G,M) \arrow{r}{\psi} \arrow[phantom, ""{coordinate, name=Z}]{d} &
H^0(G,N)
  \arrow[
    rounded corners,
    to path={
      -- ([xshift=2ex]\tikztostart.east)
      |- (Z) [near end]\tikztonodes
      -| ([xshift=-2ex]\tikztotarget.west)
      -- (\tikztotarget)
    }
  ]{dll} \\
&
H^1(G,P) \arrow{r} &
H^1(G,M) \arrow{r} &
H^1(G,N)
\end{tikzcd}

\end{document}

enter image description here

edited Jun 11 '14 at 22:12

answered Jun 11 '14 at 21:55

egreg

1,121,712

1

Is it possible to bend the arrow such that it starts at the right side of H^0(G,N) and then ends at the left side of H^1(G,P), making an inverted S shape? – Haikal Yeo Jun 11 '14 at 22:01
3

@HaikalYeo Yes, it's possible. I'm not saying I fully understand the code, I just adapted it from an example in the documentation. – egreg Jun 11 '14 at 22:13
Which documentation are you referring to? May I have the link to it? – Haikal Yeo Jun 11 '14 at 22:46
@HaikalYeo The documentation of tikz-cd; you should have it on your system, but you can find it online at http://texdoc.net/texmf-dist/doc/latex/tikz-cd/tikz-cd-doc.pdf – egreg Jun 11 '14 at 22:47
I used the exact same code but there is an additional down arrow from H^0(G,M) to H^1(G,M). How do I remove this? – Haikal Yeo Jun 12 '14 at 08:58
@HaikalYeo First of all, ensure you have an up-to-date TeX distribution – egreg Jun 12 '14 at 08:59
I'm writing this on SAGE. Is that not up to date? :/ – Haikal Yeo Jun 12 '14 at 09:02
@HaikalYeo I have no idea what you mean about SAGE; it is not a TeX distribution. What OS are you running? – egreg Jun 12 '14 at 09:04
I'm using a Mac if that's what you're asking.
https://cloud.sagemath.com/
– Haikal Yeo Jun 12 '14 at 09:05
@HaikalYeo Launch "TeX Live Utility" and do a full update. – egreg Jun 12 '14 at 09:07
How may I add in $\delta$ as a label on the longest arrow? – Haikal Yeo Aug 04 '14 at 14:46

score 8 · Accepted Answer · answered Jun 11 '14 at 23:08

8

With TikZ only

Code

\documentclass[border=2pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{matrix,quotes}
\begin{document}
\begin{tikzpicture}[scale=2]
\matrix(m)[matrix of math nodes,column sep=15pt,row sep=15pt]{
  0 & H^0(G,P) & H^0(G,M) & H^0(G,N) \\
    & H^1(G,P) & H^1(G,M) & H^1(G,N) \\
};
\draw[->,font=\scriptsize,every node/.style={above},rounded corners]
  (m-1-1) edge (m-1-2) 
  (m-1-2) edge["$\phi$"] (m-1-3)
  (m-1-3) edge["$\psi$"] (m-1-4)
  (m-1-4.east) --+(5pt,0)|-+(0,-7.5pt)-|([xshift=-5pt]m-2-2.west)--(m-2-2.west)
  (m-2-2) edge (m-2-3)
  (m-2-3) edge (m-2-4)
;
\end{tikzpicture}
\end{document}

Output

enter image description here

answered Jun 11 '14 at 23:08

Herr K.

17,946
4
61
118

How may I add in $\delta$ as a label on the longest arrow? – Haikal Yeo Aug 04 '14 at 14:46
@HaikalYeo: You can add node[pos=<num>]{$\delta$} to the 4th line after the\drawcommand. Depending on where on the line you want$\delta$to be, you may want to put thenodecode before or after the coordinates, and then usepos` to adjust its position. – Herr K. Aug 04 '14 at 20:31
Sorry if I sound really stupid here but do I replace node and num with something else? – Haikal Yeo Aug 04 '14 at 21:05
Ooh. I get it already. Except I don't know how to adjust – Haikal Yeo Aug 04 '14 at 21:07
1

@HaikalYeo: <num> is a number between 0 and 1, which controls the position of the node on a path. For example, (m-1-4.east) --+(5pt,0)|-+(0,-7.5pt)-|node[pos=.25]{$\delta$}([xshift=-5pt]m-2-2.west)--(m-2-2.west) will put the node at the middle of the longest line. – Herr K. Aug 05 '14 at 00:10

I want to draw a nice connecting homomorphism arrow

2 Answers2

Code

Output