Re: How to draw an arrow

On Oct 22, 2007, at 2:14 AM, Lawrence wrote:

> Hi all,
>
> I want to draw a phase lock ( see the plot attached) using NCL. I
> have drawn the line using "gsn_polyline", but any tips for the arrow?

Hi Lawrence,

Arrows can be drawn using the wmlabs function:

   http://www.ncl.ucar.edu/Document/Functions/Built-in/wmlabs.shtml

with the symbol set to "ARROW". The documentation in the
above is misleading - the description for "wks" should
indicate that it is the workstation where you want to
draw your symbols. Many symbols are available, arrows
being among them. See:

   http://www.ncarg.ucar.edu/ngdoc/ng/supplements/wmap/
index.html#HEADING1-90

The above documents Fortran/C interfaces, but it carries over to NCL.

For arrows, you can control size, direction, body color,
outline color, shadow color, and tail size indpendently
of the tip. Ultimately the arrows drawn come from
the wmap package. For details on arrows see:

   http://ncarg.ucar.edu/ngdoc/ng4.4/supplements/wmap/#HEADING1-102

In particular, for an explanation of the various control
parameters, visit the "table of internal parameters" link
at the above address. In NCL, values for the control
parameters can be set using the wmsetp function.

Here is a trivial NCL script that draws a couple of arrows:

load "$NCARG_ROOT/lib/ncarg/nclex/gsun/gsn_code.ncl"

;
; Draw a couple of arrows
;
begin

   wks = gsn_open_wks("x11","test_wmap")

   wmsetp("ARD",90.)
   wmlabs(wks, 0.5, 0.5, "ARROW")
   wmsetp("ARS",0.2)
   wmsetp("ARD",180.)
   wmlabs(wks, 0.5, 0.5, "ARROW")

   frame(wks)

end

Fred Clare

>
> Regards,
>
> Lawrence
>
> <arrow.jpg>
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Received on Mon Oct 22 2007 - 13:20:23 MDT