#
#  File:
#    wmbarb.py
#
#  Synopsis:
#    Draws four different wind barbs at different positions.
#
#  Category:
#    Wind barbs.
#
#  Author:
#    Fred Clare
#
#  Date of initial publication:
#    March, 2005 
#
#  Description:
#    Draws four different wind barbs at different positions.
#    Scales the sizes.
#
#  Effects illustrated:
#    o  Drawing wind barbs.
#    o  Setting and retrieving wind barb control parameters.
# 
#  Output:
#    A single visualization is produced that draws the wind barbs.
#    The retrieved control parameter WBS (for wind barb size) is
#    printed to standard output.
#
#  Notes:
#     
import Ngl

#
#  Draw four wind barbs of the same magnitude, but at different 
#  locations and in different directions.

#
#  Open a workstation.
#
wks_type = "ps"
wks = Ngl.open_wks(wks_type, "wmbarb")

#
#  Draw wind barbs.
#
x = [0.25, 0.75, 0.75, 0.25]  # x,y,u,v can also be numpy arrays.
y = [0.25, 0.25, 0.75, 0.75]
u = [50., -50., -50.,  50.0]
v = [50.,  50., -50., -50.0]
Ngl.wmsetp("wbs", 0.2)        # Scale the size.
Ngl.wmbarb(wks, x, y, u, v)   # Draw barbs.
Ngl.frame(wks)                # Draw plot.

#
#  Retrieve the value of the wbs parameter.
#
size = Ngl.wmgetp("wbs")
print "Current scale factor for wind barb size = %10.7f" % (size)

Ngl.end()