Arrows inside a commutative diagram using tikzcd

Question

\documentclass[12pt,reqno,a4paper]{amsart}
\usepackage{extsizes}
\usepackage{blindtext}
\textheight 9.3in \textwidth 6.5in
\calclayout
\usepackage{mathtools}
\usepackage{amsmath,amsthm,amsfonts,amssymb} 
\usepackage{hyperref}
\usepackage{mathrsfs}
\usepackage[all]{xy}
\usepackage[normalem]{ulem} 
\usepackage{tikz-cd}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel} 
\usepackage{color}
\pagestyle{myheadings}
\begin{document}

\begin{tikzcd}
 A \arrow[dd, "p"'] \arrow[ddrr, phantom, "\Rightarrow"] \arrow[rr, "q"] &  & B \arrow[dd, "r"] \\
 &  &  \\
 C \arrow[rr, "s"] &  & D
 \end{tikzcd}

    \begin{tikzcd}
A \arrow[dd, "p"'] \arrow[rrdd, "q"]    &  & \\
&  &                                                  \\
B \arrow[rr, "r"] &  & C                                         
\end{tikzcd}

 \end{document}

This is what I have written to get a commutative diagram.

I want to add an arrow (\Rightarrow) inside the diagram from bottom left corner to top right corner. Can some one help me to do this? I have tried to add using "phantom" but it is not coming as I expected. I want this pointing from top left corner to bottom right corner (or bottom left corner to top right corner).

Answer 1

You can shorten a Rightarrow as you like.

For the triangle, you can name the label and draw an arrow to it.

\documentclass[12pt,reqno,a4paper]{amsart}
\usepackage{tikz-cd}
\tikzcdset{row sep/normal=50pt, column sep/normal=50pt}

\begin{document}

\begin{tikzcd}
    A\arrow[d, "p"']\arrow[Rightarrow, shorten >=25pt, shorten <=25pt, dr]\arrow[r, "q"] &  B\arrow[d, "r"]\\
    C\arrow[r, "s", swap] & D
\end{tikzcd}

\begin{tikzcd}
    A\arrow[d, "p"']\arrow[r, "q"] &  B\arrow[d, "r"]\\
    C\arrow[r, "s", swap]\arrow[Rightarrow, shorten >=25pt, shorten <=25pt, ur] & D
\end{tikzcd}

\begin{tikzcd}
    A\arrow[d, "p"']\arrow[rd, "q"{name=M}] \\
    B\arrow[r, "r", swap]\arrow[Rightarrow, shorten >=10pt, shorten <=10pt, to=M] & C
\end{tikzcd}

\end{document}

Answer 2

Why not simply this, to specify the diagram commutes? Unrelated: I took the liberty to simplify your code, in particular removing unnecessary packages (already loaded by another package).

\documentclass[12pt,reqno,a4paper]{amsart}
\usepackage{extsizes}
\usepackage{blindtext}
\textheight 9.3in \textwidth 6.5in
\calclayout
\usepackage{mathtools}
\usepackage{amsthm,amssymb}
\usepackage{hyperref}
\usepackage{mathrsfs}
\usepackage[all]{xy}
\usepackage[normalem]{ulem}
\usepackage{tikz-cd}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\pagestyle{myheadings}

\begin{document}

\begin{tikzcd}[row sep = large, column sep = large]
 A \arrow[d, "p"'] \arrow[r, "q"] & B \arrow[d, "r"] \\
 C \arrow[ur, phantom, "\scalebox{1.5}{$\circlearrowleft$}" description]\arrow[r, "s"] & D
 \end{tikzcd}

 \end{document} 

Answer 3

You can use a phantom arrow, with the label in the middle via description and sloped.

\documentclass[12pt,reqno,a4paper]{amsart}
\usepackage{tikz-cd}

\begin{document}

\begin{tikzcd}[sep=huge]
A \arrow[dr,phantom,"\to" description, sloped]
  \arrow[d, "p"'] \arrow[r, "q"] & B \arrow[d, "r"] \\
C \arrow[r, "s"] & D
\end{tikzcd}

\end{document}

Answer 4

\documentclass[12pt,reqno,a4paper]{amsart}
\usepackage{extsizes}
\usepackage{blindtext}
\textheight 9.3in \textwidth 6.5in
\calclayout
\usepackage{mathtools}
\usepackage{amsmath,amsthm,amsfonts,amssymb} 
\usepackage{hyperref}
\usepackage{mathrsfs}
\usepackage[all]{xy}
\usepackage[normalem]{ulem} 
\usepackage{tikz-cd}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel} 
\usepackage{color}
\pagestyle{myheadings}
\begin{document}


\begin{tikzcd}
A \arrow[dd, "p"'] 
\arrow[rr, "q"] &  & B \arrow[dd, "r"] \\
&  &  \\
C \arrow[rr, "s"] \arrow[uurr, phantom, "\scalebox{2}{$\Rightarrow$}" description, sloped] &  & D
\end{tikzcd}.

 \end{document}

Answer 5

Here there are two version using xy package. The first mode has the classic tips (see the example below),

\documentclass[a4paper,12pt]{article}
\usepackage[all]{xy}
\usepackage{amssymb}
\newcommand{\RLongrightarrow}{\rotatebox{45}{$\Longrightarrow$}}
\usepackage{graphicx}
\begin{document}
\xymatrix@R=3pc@C=3pc{\ar @{} [dr] |{\RLongrightarrow}
A \ar[d] \ar[r] & B \ar[d] \\
C \ar[r] & D}
\end{document}

the second has the same tips of tikz-cd where I have forgotten, before, to add the labels. See the code below and the image:

\documentclass[a4paper,12pt]{article}
\usepackage[all,cmtip]{xy}
\usepackage{amssymb}
\newcommand{\RLongrightarrow}{\rotatebox{45}{$\Longrightarrow$}}
\usepackage{graphicx}
\begin{document}
\xymatrix@R=3pc@C=3pc{\ar @{} [dr] |{\RLongrightarrow}
A \ar[d]_p \ar[r]^q & B \ar[d]^r \\
C \ar[r]_s & D}
\end{document}