Adding an arrow to a knot diagram in tikz knots package

Question

How can I add an arrow to a knot diagram drawn with with tikz knots package? When I add an arrow with "decorations" tikz library to an example in this SA question I get two arrows!

\documentclass[11pt]{amsart}
\usepackage{tikz}
\usetikzlibrary{decorations.markings, arrows.meta,knots}
\begin{document}
  \begin{tikzpicture}
    \begin{knot}[clip width=10, clip radius=15pt, consider self intersections, end tolerance=3pt]
       \strand[thick, decoration={markings, mark=at position 0.6 with {\arrow{<}}},postaction={decorate}] (0,0)
          to[out=up, in=down] (0,0.7) 
          to[out=up, in=left] (0.5,1.5)
          to[out=right, in=up]  (1,1)
          to[out=down, in=right]  (0.5,0.5)
          to[out=left, in=down]  (0,1.3)
          to[out=up, in=down]  (0,2);
    \end{knot}
  \end{tikzpicture}
\end{document}

score 2 · Accepted Answer · 2020-12-14T03:29:21.923

As noted in https://tex.stackexchange.com/a/574078, you do not necessarily need decorations to add an arrow. A sloped pic also works. You can put it on the segment you want, which can be an advantage or disadvantage depending on the scenario.

\documentclass[11pt]{amsart}
\usepackage{tikz}
\usetikzlibrary{arrows.meta,knots}
\begin{document}
  \begin{tikzpicture}[pics/arrow/.style={code={%
  \draw[line width=0pt,{Computer Modern Rightarrow[line
  width=0.8pt,width=1.5ex,length=1ex]}-] (-0.5ex,0) -- (0.5ex,0);
  }}]
    \begin{knot}[clip width=10, clip radius=15pt, consider self intersections,
    end tolerance=3pt]
       \strand[thick] (0,0)
          to[out=up, in=down] (0,0.7) 
          to[out=up, in=left] (0.5,1.5)
          to[out=right, in=up]  pic[pos=0.5,sloped]{arrow}(1,1)
          to[out=down, in=right]  (0.5,0.5)
          to[out=left, in=down]  (0,1.3)
          to[out=up, in=down]  (0,2);
    \end{knot}
  \end{tikzpicture}
\end{document}

It is easy to change any aspect of the arrow. Apart from the obvious possibility of editing the pic you can just add an optional argument.

\documentclass[11pt]{amsart}
\usepackage{tikz}
\usetikzlibrary{arrows.meta,knots}
\begin{document}
  \begin{tikzpicture}[pics/arrow/.style={code={%
  \draw[line width=0pt,{Computer Modern Rightarrow[line
  width=0.8pt,width=1.5ex,length=1ex,#1]}-] (-0.5ex,0) -- (0.5ex,0);
  }}]
    \begin{knot}[clip width=10, clip radius=15pt, consider self intersections,
    end tolerance=3pt]
       \strand[thick] (0,0)
          to[out=up, in=down] (0,0.7) 
          to[out=up, in=left] (0.5,1.5)
          to[out=right, in=up]  pic[pos=0,sloped]{arrow={scale=2,line
          width=1.6pt}}(1,1)
          to[out=down, in=right]  (0.5,0.5)
          to[out=left, in=down]  (0,1.3)
          to[out=up, in=down]  (0,2);
    \end{knot}
  \end{tikzpicture}
\end{document}

Note also that sometimes one needs the allow upside down key as in https://tex.stackexchange.com/a/574078.

my apologies. I removed my answer. You made a comment on my post, which I used to make an improvement. That is how this site is supposed to work. I certainly did not copy your code or any part of your solution. There is no need for hostility in your comments. — Sandy G, Dec 14 '20 at 08:45
If the arrow is near a crossing, it ends up being behind the strands. Is there a way to fix this? — nog642, Sep 19 '23 at 05:43

Adding an arrow to a knot diagram in tikz knots package

1 Answers1