Control quiver arrow head width vs height.

Hi, I have a quiver plot where the arrow heads are incredibly wide by default, so I used "MaxHeadSize" to shrink them to a reasonable size. Also, the scaling behavior is set to 0 because I want them to connect the way they do currently. The downside is that now, instead of looking like arrowheads, they almost look like horizontal bars. I'm wondering if there is a way to control the head length independently of the head width.

[Avni Agrawal]

Hi @Patrick, can you share the code to recriprocate the issue more efficiently?

[Mathieu NOE]

seems this kind of topic has been already addressed in this forum, in some ways ... adapt to your needs

How to make the quiver() arrow head size fixed? - MATLAB Answers - MATLAB Central (mathworks.com)

Cannot set quiver head size bigger than 1/3 of the length of the arrow. - MATLAB Answers - MATLAB Central (mathworks.com)

etc...

[Patrick]

The original code depends on data external to MATLAB (Matlab calls a C function which calls other stuff to generate the data).

What I can give is a simple way to reproduce the scaling issue:

` ` `

X = 10000*rand(1, 50);

Y = [50:-1:1];

%{----------------------------------------------------------%}

%{ Generate list of steps from each "X" to the next "1" %}

%{----------------------------------------------------------%}

C = {};

D = {};

count0 = 0;

for (n = 1:length( X ))

if (X(n) >=50)

C{n-count0} = n;

else

count0 = count0 + 1;

end

end

alpha = 1;

for (n = 1:length( Y ))

D{n} = C{alpha} - n;

if (n == C{alpha})

D{n} = 0;

end

end

Y = cell2mat(D);

Z = Y;

%{---------------------------%}

%{ Create U and V arrays %}

%{---------------------------%}

E = {};

F = {};

for ( n = 2:length(X) )

if (X(n) == 1)

E{n} = 0;

else

E{n} = X(n)-X(n-1);

end

end

U = cell2mat(E);

U(end+1) = 0;

for ( n = 1:length(X) )

if (Y(n) == 0)

F{n} = 0;

else

F{n} = -1;

end

end

V = cell2mat(F);

W = V;

%% Create plots

f = figure();

f.WindowState = "maximized";

%{-----------------------------------------%}

%{ Quiver plot 1 with labels and stuff %}

%{-----------------------------------------%}

Q2A = subplot(1, 2, 1);

q2a = quiver(Y, X, U, V, 0);

q2a.MaxHeadSize = 0.1;

q2a.Marker = "*";

%{-----------------------------------------%}

%{ Quiver plot 2 with labels and stuff %}

%{-----------------------------------------%}

Q2B = subplot(1, 2, 2);

q2b = quiver(Y, X, V, U, 0);

q2b.MaxHeadSize = 0.01;

q2b.Marker = "*";

` ` `

Answer 1

[Sreeram]

Hi Patrick,

This is happening because the range of X- and Y-coordinates differ significantly. The arrow heads are scaled in relation to the range of axes.

Although I could not find any way to adjust arrow’s head length independent of head width, you can follow the workaround by the MathWorks Support Team here:

https://www.mathworks.com/matlabcentral/answers/95537

Here’s how I implemented it:

scale_factor = range(Y)/range(X);
q2b = quiver(Y, X*scale_factor, V, U*scale_factor, 0);
q2b.Marker = "*";
ytlbls=Q2B.YTickLabel;
ytlbls=cellfun(@(c)str2double(c)/scale_factor,ytlbls);
set(Q2B,'YTickLabel',ytlbls)

Here’s a comparison of before and after for the second subplot (which had arrows appearing as horizontal line):

Before

After

I hope it helps!