subr PLOT_ARROWS,IXB,IYB,DX,DY,SIZE
 ;originally written by SHF prior to 4/89
 ;4/13/89  r. shine
 ;11/23/95 modified to use xdrawline routine and pixel coordinates
 IF !NARG LT 5 THEN SIZE=0.3
 ;puts up a bunch of vectors, arguments are one-d arrays
 ;first set (IXB,IYB) is base and (DX,DY) is vector
 SPHI=.316
 CPHI=.949
 nx = dimen(ixb,0)	ny = dimen(ixb,1)
 
 n = nx*ny
 ix2 = ixb +dx		iy2 = iyb + dy
 xdrawline, ixb, iyb, ix2, iy2
 sq = sqrt(dx*dx+dy*dy)
 sqi = 1/sq
 zips = sieve(sq eq 0.0)
 sqi(zips) = 0
 zq = size*sqi
 xdrawline, ix2, iy2, ix2-zq*(cphi*dx-sphi*dy), iy2-zq*(cphi*dy+sphi*dx)
 xdrawline, ix2, iy2, ix2-zq*(cphi*dx+sphi*dy), iy2-zq*(cphi*dy-sphi*dx)
 xflush
 endsubr