tikz-arrowstikz-cd
I have the following diagram:
\begin{tikzcd}[font=\large]
A \rightarrow & B & C \leftarrow & D\\
E \arrow[hookrightarrow]{u} \rightarrow & F \arrow{ru} & G \leftarrow \arrow{ru}
\end{tikzcd}
Is there a way of "drawing" a longer arrow in the 2nd row such that F is below C and G is below D?
The package documentation contains examples of most of this. Section 1.1 gives examples for placing of labels, Section 2 provides ways to adjust the appearence of the diagram and control spacing. However, the package documentation is easiest to understand in conjunction with the manual for tikz and its underlying language pgf: see http://www.ctan.org/pkg/pgf in particular section 16.8 Placing Nodes on a Line or Curve Explicitly.
By default labels on arrows are to the left of the direction of travel. This my be changed by prefixing the label with [swap], so you can write \arrow{r}{a}[swap]{b} to get an arrow to the right with label a above and b below.
[Code at end.]
Diagrams are set on a grid, so you can't make more space for a single arrow. However, you can open up the grid horizontally and vertically (if necessary with different factors).
Basic tikz options such as for placing labels along the arrow are [pos=0.7] for 0.7 of the way along the length and [near start]/[near end] for near to the beginning or the end.
Labels may be turned with [rotate=90], or some other angle. Doing this you will often need to shift the label with the options xshift or yshift, as in the example above, where one could write
\arrow{d}[anchor=center,rotate=-90,yshift=1ex]{\text{arrow name}}
However, as Qrrbrbrilbel points out it is easier to use sloped together with above or below as in the code below (swap no longer has an effect).
\documentclass{article}
\usepackage{tikz-cd}
\usepackage{mathtools}
\begin{document}
\begin{displaymath}
\begin{tikzcd}
x \arrow{r}{a} \arrow{d}[swap]{b} &y \arrow{d}{d} \\
z \arrow{r}{e}[swap]{c} &w \\
\end{tikzcd}
\end{displaymath}
\begin{displaymath}
\begin{tikzcd}[column sep=6em,row sep=6em]
x \arrow{r}{\text{arrow name}}
\arrow{d} &y \arrow{d}[sloped,above]{\text{arrow
name}} \\
z \arrow{r} &w \\
\end{tikzcd}
\end{displaymath}
\end{document}
If you need a non-grid layout then as in section 3.3 of the manual, you need to resort to basic tikz to place elements.
You can try the dynkin-diagrams package. This example is included in the documentation. Note that by default, the affine root of this D series diagram is marked with a white circle, while the other roots have solid circles; you can easily change this if you don't like it.
\documentclass{amsart}
\usepackage{dynkin-diagrams}
\tikzset{big arrow/.style={
-Stealth,line cap=round,line width=1mm,
shorten <=1mm,shorten >=1mm}}
\newcommand\catholic[2]{\draw[big arrow,green!25!white]
(root #1) to (root #2);}
\newcommand\protestant[2]{
\begin{scope}[transparency group, opacity=.25]
\draw[big arrow,orange] (root #1) to (root #2);
\end{scope}}
\begin{document}
\begin{dynkinDiagram}[edge length=1.2cm,
indefinite edge/.style={thick,loosely dotted},
labels*={0,1,2,3,\ell-3,\ell-2,\ell-1,\ell}]{D}[1]{}
\catholic{0}{6}\catholic{1}{7}
\protestant{7}{0}\protestant{6}{1}
\end{dynkinDiagram}
\end{document}
Best Answer
Do you want this? Your question is not very clear.