19

How to put a square inside a commutative diagram as in the following picture:

enter image description here

It would like to have a square in the following diagram:

\documentclass[a4paper,12pt]{article}
\usepackage{tikz-cd}
\begin{document}

\begin{tikzcd}
X\times_S Y \arrow{r}{p_2} \arrow{d}[swap]{p_1} &Y \arrow{d}{g} \\   
X \arrow[swap]{r}{f} & Z
\end{tikzcd}
        
\end{document}
1
  • 2
    Welcome to TeX.SX! Please help us help you and add a minimal working example (MWE) that illustrates your problem. Reproducing the problem and finding out what the issue is will be much easier when we see compilable code, starting with \documentclass{...} and ending with \end{document}. Commented Apr 24, 2017 at 8:59

3 Answers 3

10

Two solutions: one with pstricks and a psmatrix environment, the other with tikz-cd, in which I use the short syntax for arrows:

\documentclass{article}
\usepackage{mathtools, amssymb}
 \usepackage{pst-node, auto-pst-pdf}
\usepackage{tikz-cd}

\begin{document}

\texttt{psmatrix solution: }
 \[ \psset{arrows=->, arrowinset=0.15, linewidth=0.6pt, nodesep=3pt, rowsep=0.6cm, colsep = 1cm}
 \everypsbox{\scriptstyle}
 \begin{psmatrix}
%%% nodes
  X'' & X' & X \\%
S'' & S' & S
 %%% horizontal arrows
\ncline{1,1}{1,2}\naput{g'} \ncline{1,2}{1,3}\naput{g}
 \ncline{2,1}{2,2}\nbput{f'} \ncline{2,2}{2,3}\nbput{f}
 %%% vertical arrows
\ncline{1,1}{2,1} \ncline{1,2}{2,2}\ncline{1,3}{2,3}
\ncline[linestyle =none, arrows=-]{1,2}{2,3}\ncput{\textstyle\square}
 \end{psmatrix}
 \]
\vskip 1cm

\texttt{tikz-cd solution: }
\[ \begin{tikzcd}[arrows={-Stealth}]
  X''\rar["g'"]\dar & X'\rar["g"]\dar\drar[phantom, "\square"] & X\dar \\%
S''\rar[swap, "f'"] & S'\rar[swap, "f"] & S
\end{tikzcd}
\]

\end{document} 

enter image description here

24

The right way with tikz-cd is to use a "phantom" arrow as in

\arrow[dr, phantom, "\square"]

MWE (I've used some code to reproduce the picture and not yours):

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

\begin{document}

\begin{tikzcd}
X'' \arrow[r, "g'"] \arrow[d] & X' \arrow[r, "g"] \arrow[d] \arrow[dr, phantom, "\square"] & X \arrow[d] \\
S'' \arrow[r, "f'"']          & S' \arrow[r, "f"']                                         & S
\end{tikzcd}

\end{document} 

enter image description here

2

Another solution could be to use execute at end picture.
It is less elegant than karlkoeller's answer, but it allows you to position the node wherever you like, just changing its coordinates.

\documentclass[a4paper,12pt]{article}
\usepackage{amssymb}
\usepackage{tikz-cd}
\usetikzlibrary{calc}

\begin{document}

\begin{tikzcd}[
    every matrix/.append style={name=mycd},
    execute at end picture={
    \node at ($(mycd-1-1)!0.5!(mycd-2-2)$) {$\square$};
    }
]
X\times_S Y \arrow{r}{p_2} \arrow{d}[swap]{p_1} &Y \arrow{d}{g} \\   
X \arrow[swap]{r}{f} & Z
\end{tikzcd}

\end{document}

enter image description here

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .