Updownarrows in commutative diagrams

Question

Can anybody tell me how to draw a diagram from A to B with an uparrow and a downarrow? Thanks.

For a start: see http://tex.stackexchange.com/q/122775/34618 — Jesse, May 27 '14 at 07:34

score 1 · Accepted Answer · answered May 27 '14 at 08:10

1

Here's an example:

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

\begin{document}

\[
\begin{tikzcd}
A \arrow[shift right=.3em,swap]{d}{f} \\ % arrow down, labeled f
B \arrow[shift right=.3em,swap]{u}{g}    % arrow up, labeled g
\end{tikzcd}
\]

\end{document}

enter image description here

Some points to notice:

Left and right are with respect to an imaginary travel from the source to the target of the arrow;
shift right means move the arrow towards the right (as determined by the rule above;
the label is placed by default on the left side, but swap orders to change side.

The alternative format

\begin{tikzcd}
A \arrow[shift left=.3em]{d}{f} \\ % arrow down, labeled f
B \arrow[shift left=.3em]{u}{g}    % arrow up, labeled g
\end{tikzcd}

which produces

enter image description here

should visually explain what is meant by the rules above.

The direction indicators are d, u, l and r and combinations thereof.

answered May 27 '14 at 08:10

egreg

1,121,712

Thanks very much. But when I try to use the package{tikz-cd}, an error appears, saying there is no room for a new \dimen. – ksj03 May 27 '14 at 11:16
@ksj03 That can happen; add \usepackage{etex} just after the \documentclass line. See No room for a new \dimen – egreg May 27 '14 at 11:24
It still doesn't work! – ksj03 May 27 '14 at 12:29
It seems that there is something wrong with pgfkeys. I don't know why. – ksj03 May 27 '14 at 12:33

Updownarrows in commutative diagrams

1 Answers1