arrows

 function [h]=arrows(x,y,w,fac,color)
    Draws arrows with their tails at each point corresponding
    to identical indices in the matrices x,y.  The matrices u
    and v are the components of the vector to be represented.
    fac is the scaling factor 

  Geometry of arrowheads (choosing HEADA and HEADL):
    If the arrow is defined by the points A B C B D where A is the base of 
  the arrow, B is the head, and C and D are the corners of the arrowhead, then
  HEADA is the angle BAC (or BAD), and HEADL is the ratio of distances AC/AB.

0001 function [h]=arrows(x,y,w,fac,color)
0002 % function [h]=arrows(x,y,w,fac,color)
0003 %    Draws arrows with their tails at each point corresponding
0004 %    to identical indices in the matrices x,y.  The matrices u
0005 %    and v are the components of the vector to be represented.
0006 %    fac is the scaling factor
0007 %
0008 %  Geometry of arrowheads (choosing HEADA and HEADL):
0009 %    If the arrow is defined by the points A B C B D where A is the base of
0010 %  the arrow, B is the head, and C and D are the corners of the arrowhead, then
0011 %  HEADA is the angle BAC (or BAD), and HEADL is the ratio of distances AC/AB.
0012 %
0013 
0014 % revision 3/20/97 to use nans for line breaks
0015 % much more efficient and returns only a single handle
0016   
0017 HEADA=10*pi/180; HEADL=.75;
0018 z=x(:)+i*y(:);
0019 
0020 if nargin < 5,color='red';end
0021 if nargin < 4,help arrows,end
0022 w=w(:)*fac;
0023 r=w*HEADL; wr1=r*exp(+i*HEADA); wr2=r*exp(-i*HEADA);
0024 wplot=ones(length(z),6); 
0025 wplot(:,1)=z; 
0026 wplot(:,[2,4])=(z+w)*ones(1,2);
0027 wplot(:,3)=z+wr1; wplot(:,5)=z+wr2;
0028 wplot(:,6)=z*nan;
0029 wplot=wplot.';
0030 wplot=wplot(:);
0031 %z=eps*ones(size(wplot));
0032 %h=line(real(wplot),imag(wplot),z,'color',color);
0033 h=line(real(wplot),imag(wplot),'color',color);
0034 set(h(1),'userdata',fac);