/usr/share/freemat/toolbox/graph/quiver.m is in freemat-data 4.0-5.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 | % QUIVER Quiver plot
% QUIVER(X,Y,U,V) plots velocity vectors as arrows with components (u,v)
% at the points (x,y). QUIVER automatically
% scales the arrows to fit within the grid.
%
% QUIVER(U,V) plots velocity vectors at equally spaced points in
% the x-y plane.
%
% QUIVER(U,V,S) or QUIVER(X,Y,U,V,S) automatically scales the
% arrows to fit within the grid and then stretches them by S. Use
% S=0 to plot the arrows without the automatic scaling.
%
% QUIVER(...,LINESPEC) uses the plot linestyle specified for
% the velocity vectors.
% Fixme: when use quiver() with hold on after image(), the two plots seems
% using different axis system.
function h = quiver(varargin)
scale = 1;
if nargin == 2 || nargin == 3
u = varargin{1};
v = varargin{2};
[x, y] = meshgrid(1:size(u,2), 1:size(u,1));
if nargin ==3 && isnumeric(varargin{3})
if varargin{3} == 0
scale = 0;
else
scale = varargin{3};
end
varargin(3) = [];
end
varargin(1:2) = [];
elseif nargin >= 4
x = varargin{1};
y = varargin{2};
u = varargin{3};
v = varargin{4};
if nargin >=5 && isnumeric(varargin{5})
if varargin{5} == 0
scale = 0;
else
scale = varargin{5};
end
varargin(5) = [];
end
varargin(1:4) = [];
else
error('Quiver needs at least 2 arguments')
end
len = sqrt(u(:).^2+v(:).^2);
if scale ~= 0
len = 0.7*scale*len*sqrt(max(x(2:end)-x(1:end-1))^2+max(y(2:end)-y(1:end-1))^2)/max(len(:));
end
phi = atan2(v(:),u(:));
if isempty(varargin)
varargin = {'b-'};
end
t1 = len.*cos(phi);
t2 = len.*sin(phi);
h1 = plot([x(:), x(:)+t1]', [y(:), y(:)+t2]', varargin{:});
hold on
h2 = plot([x(:)+t1-0.2*len.*cos(phi-pi/8), x(:)+t1, x(:)+t1-0.2*len.*cos(phi+pi/8)]', ...
[y(:)+t2-0.2*len.*sin(phi-pi/8), y(:)+t2, y(:)+t2-0.2*len.*sin(phi+pi/8)]', varargin{:});
hold off
if nargout > 0
h = [h1 h2];
end
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