[Tex/LaTex] On arrows in Tikz cd

arrowsdiagramstikz-pgf

So I am getting used to using tikz-cd package to draw relatively straightforward commutative diagrams. I have two questions.

Question 1 Here is the code:

\documentclass[10pt, draft]{amsart}
\usepackage{pgf}
\usepackage{tikz}
\usepackage{tikz-cd}
\usetikzlibrary{arrows, matrix}
% With tons of other packages not relevant here I guess
\begin{document}
 % With some text ....
\[ 
\begin{tikzcd}
Y \arrow[dashrightarrow]{d} \arrow{rd} &  \\
Y_{0} \arrow{r}{\pi_{0}} & X \\
\end{tikzcd}
\]
\end{document}

What happens here is that the arrow tips for the diagonal arrow is extremely light compared to the other two, you can see that in the picture below. I would like to know how to fix that.
enter image description here

Question 2 In the following diagram, (which also suffers from the same issues of question 1 above), I would want to fix the hook on the arrow labelled i so that it points the correct way (and perhaps make it more prominent).

enter image description here

Here is the code I am using for that part.

  \[
  \begin{tikzcd}[column sep =small] 
   & (X_{0},x)\arrow[hookrightarrow]{dl}{i}\arrow[hookrightarrow]{dr}{i^{\prime}}
     &   \\  
   (X,x) \arrow{dr} \arrow{rr}
   & & (X^{\prime}, x) \arrow{dl} \\
   & (U,u)
     & 
  \end{tikzcd}
  \]

Best Answer

The thickness problem seems to be a viewer issue. For the hook in the second diagram you can use a direct TikZ expression for the arrow; with the key swap you can change the side of the arrow chosen for the label.

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

\begin{document}
\[
\begin{tikzcd}[column sep=small] 
&  
  (X_{0},x) 
  \arrow[hookrightarrow]{dr}{i'}
  \arrow[left hook->,swap]{dl}{i} % <-- reflect the direction of the hook
\\
(X,x)
  \arrow{dr} \arrow{rr} 
&&
(X', x)
  \arrow{dl} \\
&
(U,u)  
\end{tikzcd}
\]
\end{document}

It's easier to type i' for i^{\prime} and the output is exactly the same. Never leave blank lines in the code for a tikzcd.

enter image description here

Related Solutions

[Tex/LaTex] Drawing Multiple Diagonal Arrows in a Table

You can place, for each arrow, two nodes (one to signal the start, and the other one the end) and then use a loop to connect each pair of nodes:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc,arrows}

\newcommand{\tikzmark}[1]{%
  \tikz[overlay,remember picture] \node (#1) {};}

\begin{document}

\[
\begin{array}{*{6}{c}}
E_{1} & = & \tikzmark{e1}x_{1}^1\tikzmark{s1} & x_{1}^2\tikzmark{s2} & x_{1}^3\tikzmark{s3} & ... \\
\\
E_{2} & = & \tikzmark{e2}x_{2}^1 & x_{2}^2 & x_{2}^3\tikzmark{s4} & ... \\
\\
E_{3} & = & \tikzmark{e3}x_{3}^1 & \tikzmark{e4}x_{3}^2 & \tikzmark{e5}x_{3}^3\tikzmark{s5} & ... \\
... \\
\end{array}
\]
\begin{tikzpicture}[overlay,remember picture]
\foreach \i in {1,2,...,5}
  \draw[->] ($(s\i.north east)+(-0.1,0.1)$) -- ($(e\i.south west)+(0.1,0)$);
\end{tikzpicture}

\end{document}

enter image description here

As the above image shows, the lines are not parallel; to correct this, perhaps the fastest way is to use a matrix of nodes:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{matrix}

\begin{document}

\begin{tikzpicture}
\matrix[matrix of math nodes,inner sep=1pt,row sep=1em,column sep=1em] (M)
{
    E_1 & = & x_{1}^{1} & x_{1}^{2} & x_{1}^{3}  & \cdots \\
    E_2 & = & x_{2}^{1} & x_{2}^{2} & x_{2}^{3}  & \cdots \\
    E_3 & = & x_{3}^{1} & x_{3}^{2} & x_{3}^{3}  & \cdots \\
    \cdots \\
}
;
\draw[->] (M-1-3.north east) -- (M-1-3.south west);
\draw[->] (M-1-4.north east) -- (M-2-3.south west);
\draw[->] (M-1-5.north east) -- (M-3-3.south west);
\draw[->] (M-1-3.north east) -- (M-1-3.south west);
\draw[->] (M-2-5.north east) -- (M-3-4.south west);
\draw[->] (M-3-5.north east) -- (M-3-5.south west);
\end{tikzpicture}

\end{document}

enter image description here

[Tex/LaTex] How to vertically align the labels in a tikz diagram

As I told you in my comment you need to set an horizontal line. I selected f_2 as a reference point and named it while placing on the path

\draw[arr] (m-1-3) -- node[description] (f2) {$f_2$} (m-2-3)

the horizontal line crossing f2 is declared with

\path[name path=pf2] (m-1-1|-f2)--(m-1-4|-f2);

Then you need to name all other paths like

\draw[arr,name path=pf0] (m-1-1) -- (m-2-3);

and place labels over intersections

\node[arr,description,name intersections={of=pf0 and pf2}] (f0) at (intersection-1) {$f_0:=f$};

My complete code is

\documentclass[border=1]{standalone}
\usepackage{tikz}
\usetikzlibrary{matrix,arrows,intersections}

\begin{document}

\begin{tikzpicture}
[
  arr/.style={->,font=\scriptsize},
  description/.style={fill=white,inner sep=2pt}
]
\matrix (m) [
  matrix of math nodes, row sep=3em, column sep=4em, text height=1.5ex, text depth=0.25ex
] 
{A[f]_0:=A & A[f]_1 & A[f]_2 & \cdots \\
                    &        & B      \\};
\draw[arr] (m-1-1) -- node[above]       {$\pi_0$}  (m-1-2); 
\draw[arr] (m-1-2) -- node[above]       {$\pi_1$}  (m-1-3);
\draw[arr] (m-1-3) -- node[above]       {$\pi_2$}  (m-1-4);

\draw[arr] (m-1-3) -- node[description] (f2) {$f_2$}    (m-2-3);
\draw[arr,name path=pf0] (m-1-1) -- (m-2-3);
\draw[arr,name path=pf1] (m-1-2) -- (m-2-3);
\draw[arr,name path=pf3] (m-1-4) -- (m-2-3);
\path[name path=pf2] (m-1-1|-f2)--(m-1-4|-f2);
\draw[red] (m-1-1|-f2)--(m-1-4|-f2);

\node[arr,description,name intersections={of=pf0 and pf2}] (f0) at (intersection-1) {$f_0:=f$};
\node[arr,description,name intersections={of=pf1 and pf2}] (f1) at (intersection-1) {$f_1$};
\node[arr,description,name intersections={of=pf3 and pf2}] (f3) at (intersection-1) {$f_3$};
\end{tikzpicture}

\end{document}

and the result

enter image description here

Best Answer

Related Solutions

[Tex/LaTex] Drawing Multiple Diagonal Arrows in a Table

[Tex/LaTex] How to vertically align the labels in a tikz diagram

Related Question