Quiver plot with pgfplots: scale arrowheads with arrowsize

Question

It is my understanding that the quiver plot with pgfplots keeps a constant arrowhead size, irrespective of the size (should I say length) of the arrow itself. Is there a way to have the arrowhead size linearly depending on the length of the arrow?

\documentclass[10pt,tikz]{standalone}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{pgfplots}
\usetikzlibrary{arrows.meta}
\begin{document}
\begin{tikzpicture}[scale=1]
\begin{axis}[domain=-3:3, view={0}{90}]
\addplot3[Couleur, quiver={u=-x, v={-y},scale arrows=0.085},-{Latex[width=2pt,length=3pt]},samples=21] {0};
\end{axis}
\end{tikzpicture}
\end{document}

EDIT: A possible solution is given below but it is not really convincing because the arrowhead size is hard to control. Furthermore, the line thickness is almost zero in the center of the figure while arrowheads do not vanish.

\documentclass[10pt,tikz]{standalone}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{pgfplots}
\begin{document}
\begin{tikzpicture}[scale=1]
\def\U{-x}\def\V{-y}\def\LEN{(sqrt((\U)^2 + (\V)^2)}
\begin{axis}[axis equal,view={0}{90}]
\addplot3[blue,point meta={\LEN},quiver={u={(\U)},v={(\V)},scale arrows=.15,every arrow/.append style={line width=\pgfplotspointmetatransformed/1000 * .5pt}},- latex,samples=24] {0};
\end{axis}
\end{tikzpicture}
\end{document}

enter image description here

See How can I draw a quiver plot with varying line thickness? for a way of scaling the line width and arrowhead size of quiver plots. — Jake, Oct 23 '14 at 12:30
@Jake Thanks. It looks like a duplicate then. I could not find it. — pluton, Oct 23 '14 at 13:05
I wouldn't say it's a duplicate, since that answer also scales the width of the arrow line, not just the size of the head. — Jake, Oct 23 '14 at 13:06
@Jake maybe I could use something in the line of -{Latex[width=\pgfplotspointmetatransformed/1000*2pt,length=\pgfplotspointmetatransformed/1000*3pt]} to scale the arrowhead only. I'll try later. Scaling the arrow line as well is fine with me. — pluton, Oct 23 '14 at 13:09
What I said above does not seem to be working. I cannot really say why. — pluton, Oct 24 '14 at 00:37

score 9 · Accepted Answer · edited Jun 10 '20 at 12:32

9

The approach suggested by @Jake is the right direction. Unfortunately, -{Latex[width=...]} causes strange problems when used insided of every arrow. It appears that this kind of arrow key reconfiguration is unsupported. I will look into it eventually, sounds like some incompatibility between the arrows.meta library and pgfplots.

But it works if you use scale length which appears to be better suited anyway:

\documentclass{standalone}
\usepackage{pgfplots}
\pgfplotsset{compat=1.10}
\usetikzlibrary{arrows.meta}
\begin{document}
\begin{tikzpicture}
\begin{axis}[domain=-3:3, view={0}{90}]
\addplot3[blue,
    point meta={sqrt(x^2+y^2)},
    quiver={
        u=-x, 
        v={-y},
        scale arrows=0.085,
        every arrow/.append style={%
            -{Latex[scale length={max(0.1,\pgfplotspointmetatransformed/1000)}]},
        },
    },
    samples=21,
] 
    {0};
\end{axis}
\end{tikzpicture}
\end{document}

enter image description here

The idea as such is similar to that of How can I draw a quiver plot with varying line thickness? : we define point meta to resemble the vector length. Then we scale every arrow by \pgfplotspointmetatransformed/1000. Keep in mind that \pgfplotspointmetatransformed is a number in the range [0,1000]; it is the result of mapping the value of point meta into that range. Since scale length=0 is illegal, we have to introduce a lower limit here.

edited Jun 10 '20 at 12:32

Community

1

answered Nov 02 '14 at 19:11

Christian Feuersänger

55,840

ok thanks: it looks promising. One comment: the arrow in the middle "should" disappear. I guess it is impossible to achieve because of the illegal scale length=0. – pluton Nov 04 '14 at 13:15
I see. What if you use 0.01 as smallest possible scale? It looks like a dot... – Christian Feuersänger Nov 04 '14 at 21:24
Will you keep us posted when you update pgfplots (if you do)? Thanks – pluton Nov 10 '14 at 14:12
@pluton I suppose the next update will be at the end of 2014. – Christian Feuersänger Nov 10 '14 at 19:19
This seems only to "flatten" the arrowheads; I.e. the scaling is not uniform...arrows are scaled only in the direction parallel to the arrow. Is that intended? Is it possible to scale uniformly? – Chris Chudzicki Mar 01 '16 at 19:26
@mrc I may be able to look into it eventually, but I suggest that you file a new question. – Christian Feuersänger Mar 29 '16 at 17:49

Quiver plot with pgfplots: scale arrowheads with arrowsize

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