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Re: headless vectors?




Hi Billy,
	I don't know how to turn off the barbs on vectors, but at various
times I have drawn headless vectors using ppl plotuv or by writing then
rereading a file with the necessary coordinates.

	Here is an easy way that may suit your purpose using ppl+ aline.

use etopo20 ; region/x=180:270/y=45:60 ; fill/nokey rose

can region

def axis/x=190:300:10 xax ; def axis/y=46:58:2 yax
def grid/x=xax/y=yax grd
let xx=x[g=grd]+y[g=grd]-y[g=grd] ; let yy=y[g=grd]+x[g=grd]-x[g=grd]

! now xx,yy is a 2-d array of points where the headless vectors originate

! next define the tails of the arrows (taking care to get the aspect ratio
! right for your underlying plot).  I'll demonstate with uniform arrows.

(I meant to say "head" in the last comment)

let xh=xx+0.707 ; let yh=yy+0.707

sp touch alines.jnl ! prepare a file to accept the aline info

list/nohead/i=1:5/j=1:3/app/file=alines.jnl 
           /form=('ppl aline 1',4f8.3) xx,yy,xh,yh

go alines

Mick
PS you can use ppl pen ... to select the headless arrow color


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