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#!/usr/bin/env python
"""Extension of matplotlib's arrows to give additional control.
Contributed this back to the matplotlib developers, so may be obsolete.
"""
from matplotlib.patches import Polygon
from numpy import dot, array, sqrt, concatenate
__author__ = "Rob Knight"
__copyright__ = "Copyright 2007-2009, The Cogent Project"
__credits__ = ["Rob Knight"]
__license__ = "GPL"
__version__ = "1.4.1"
__maintainer__ = "Rob Knight"
__email__ = "rob@spot.colorado.edu"
__status__ = "Production"
class FancyArrow(Polygon):
"""Like Arrow, but lets you set head width and head height independently."""
def __init__(self, x, y, dx, dy, width=0.001, length_includes_head=False, \
head_width=None, head_length=None, shape='full', overhang=0, \
head_starts_at_zero=False,**kwargs):
"""Returns a new Arrow.
length_includes_head: True if head is counted in calculating the length.
shape: ['full', 'left', 'right']
overhang: distance that the arrow is swept back (0 overhang means
triangular shape).
head_starts_at_zero: if True, the head starts being drawn at coordinate
0 instead of ending at coordinate 0.
"""
if head_width is None:
head_width = 3 * width
if head_length is None:
head_length = 1.5 * head_width
distance = sqrt(dx**2 + dy**2)
if length_includes_head:
length=distance
else:
length=distance+head_length
if not length:
verts = [] #display nothing if empty
else:
#start by drawing horizontal arrow, point at (0,0)
hw, hl, hs, lw = head_width, head_length, overhang, width
left_half_arrow = array([
[0.0,0.0], #tip
[-hl, -hw/2.0], #leftmost
[-hl*(1-hs), -lw/2.0], #meets stem
[-length, -lw/2.0], #bottom left
[-length, 0],
])
#if we're not including the head, shift up by head length
if not length_includes_head:
left_half_arrow += [head_length, 0]
#if the head starts at 0, shift up by another head length
if head_starts_at_zero:
left_half_arrow += [head_length/2.0, 0]
#figure out the shape, and complete accordingly
if shape == 'left':
coords = left_half_arrow
else:
right_half_arrow = left_half_arrow*[1,-1]
if shape == 'right':
coords = right_half_arrow
elif shape == 'full':
coords=concatenate([left_half_arrow,right_half_arrow[::-1]])
else:
raise ValueError, "Got unknown shape: %s" % shape
cx = float(dx)/distance
sx = float(dy)/distance
M = array([[cx, sx],[-sx,cx]])
verts = dot(coords, M) + (x+dx, y+dy)
Polygon.__init__(self, map(tuple, verts), **kwargs)
def arrow(axis, x, y, dx, dy, **kwargs):
"""Draws arrow on specified axis from (x,y) to (x+dx,y+dy)."""
a = FancyArrow(x, y, dx, dy, **kwargs)
axis.add_artist(a)
return a
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