>
> Hi there,
>
> I was wondering if it is possible to use say gsn_polyline to draw an
> arrow.
>
> that is, is it possible to put an arrowhead on the end of a line?
>
> thanks,
> jason
Hi Jason,
It is not possible to draw arrows using gsn_polyline, other than
drawing each individual edge.
However, you can use the function "wmlabs" which is part of the
weather map package that allows you to draw all kinds of weather
symbols, arrows included. I'll include a short sample script
below. Here's the URL for the documentation for wmlabs:
http://ngwww.ucar.edu/ngdoc/ng/ref/ncl/functions/wmlabs.html
--Mary
load "$NCARG_ROOT/lib/ncarg/nclex/gsun/gsn_code.ncl"
begin
;
; Define a color map and create an X11 workstation.
;
cmap = (/ \
(/ 1., 1., 1. /), \ ; color index 0 - white
(/ 0., 0., 0. /), \ ; color index 1 - black
(/ 1., 1., 0. /), \ ; color index 2 - yellow
(/ 0., 0., 1. /) \ ; color index 3 - blue
/)
wks = gsn_open_wks("x11","arrow")
gsn_define_colormap(wks,cmap)
;
; Create arrays to hold random arrow positions.
;
nums = 200
x = new(nums,float)
y = new(nums,float)
s = new(nums,float)
;
; Draw some arrows at random positions and with random sizes
; and directions.
;
wmsetp("awc",2) ; arrow color
wmsetp("aoc",3) ; outline color
do i=0,nums/2
x(i) = rand()/32767.
y(i) = rand()/32767.
deg = 360.*rand()/32767.
size = 0.1*rand()/32767.
wmsetp("ard",deg) ; random direction
wmsetp("ars",size) ; random size
wmlabs(wks, x(i), y(i), "arrow") ; Draw arrows.
end do
frame(wks) ; Advance the frame.
end
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