## Copyright (C) 2006 G. D. McBain
##
## This program is free software.

## -*- texinfo -*- 
## @deftypefn {Function File} {} qquiver (@var{x}, @var{y}, @var{u}, @var{v}, @var{dt})
## Plot the vector field with components @address@hidden@var{dt}} and
## @address@hidden@var{dt}} at @var{x} and @var{y}.
## @end deftypefn

## Author: G. D. McBain <address@hidden>
## Created: 2006-08-10
## Keywords: plotting, vector fields, direction, arrow, quiver

function qquiver (x, y, u, v, dt)
  n = length (x(:));
  x1 = x + u*dt;
  y1 = y + v*dt;
  arrowx = reshape ([x(:)'; x1(:)'; (NaN (1, n))], [3*n, 1]);
  arrowy = reshape ([y(:)'; y1(:)'; (NaN (1, n))], [3*n, 1]);
  plot (x, y, "*;;g", arrowx, arrowy, "-;;r");
endfunction