# Making diagrams

I'm interested in making a type diagram:

I have the following commands:

\begin{equation*}
\xymatrix@C+1em@R+1em{
\A \ar[r]^-{f} \ar[d]_-{g} & B \\
\C \ar[ur]_-{h}}
\end{equation*}


Who provided me with:

What should I change to do the first diagram?

Thanks

• Hint: you need 3 columns, 2 rows. C should be in the 2nd row, 2nd column. Then, change the arrow directions accordingly. – Sigur Nov 16 '18 at 17:53
• Why not use tikz-cd? – murray Nov 16 '18 at 20:39

Welcome to TeX.SE! If you are not insisting on xymatrix, you could try

\documentclass{amsart}
\usepackage{tikz-cd}
\begin{document}
$\begin{tikzcd}[row sep=4em] A \arrow[rr, "f"] \arrow[rd, "g"swap]& & B\\ & C \arrow[ur, "h"swap] & \end{tikzcd}$
\end{document}


EDIT: switched to relativistic ;-) units, big thanks to @egreg.

• I'm not a fan of absolute length such as 1.2cm, for these cases. – egreg Nov 16 '18 at 18:29
• @egreg Morally I agree but do you really want to add an empty line instead? – marmot Nov 16 '18 at 18:30
• I suggest using relative units such as em or ex. – egreg Nov 16 '18 at 21:06
• Sorry for the basic question, but isn't the relative unit convertible to cm for example in the end? – Diaa Nov 18 '18 at 6:00

Using the xymatrix package you can see an example of little guide for this package: https://www.jmilne.org/not/Mxymatrix.pdf. I have created with this package, for your request, a simple code.

Picture with equilateral triangle.

\documentclass[a4paper,12pt]{article}
\usepackage[all]{xy}
\begin{document}
\xymatrix@C-=0.5cm{
A
\ar@{->}[rr]^f \ar@{->}[rd]_g & & B \ar@{<-}[ld]^h\\
&C&\\
&&
}
\end{document}

• It is not necessary to use @{->} since it is the standard arrow style. – Sigur Nov 17 '18 at 21:00
• Why empty 3rd line in the second example? – Sigur Nov 17 '18 at 21:01
• Although it is not wrong, it is not so natural to insert an arrow from B to C with reversed tip at the starting point. It is easier to read the code if the arrow starts from C. – Sigur Nov 17 '18 at 21:11
• I've done a lot of rehearsals reading the guide. And to have an equilateral triangle with no errors in the compilation I have inserted the third empty line and I must necessarily use @{->}. I have tried to do my best, I can assure you. – Sebastiano Nov 17 '18 at 21:11
• I don't know the difference between @C and @C-. Also, if you use column distance equal to half centimeter, you have to be sure that the diagonal arrows also have such length. There is @R also. – Sigur Nov 17 '18 at 21:16