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import matplotlib.pyplot as plt
from matplotlib import collections, transforms
from matplotlib.colors import colorConverter
import numpy as np
nverts = 50
npts = 100
# Make some spirals
r = np.array(range(nverts))
theta = np.array(range(nverts)) * (2*np.pi)/(nverts-1)
xx = r * np.sin(theta)
yy = r * np.cos(theta)
spiral = list(zip(xx,yy))
# Make some offsets
rs = np.random.RandomState([12345678])
xo = rs.randn(npts)
yo = rs.randn(npts)
xyo = list(zip(xo, yo))
# Make a list of colors cycling through the rgbcmyk series.
colors = [colorConverter.to_rgba(c) for c in ('r','g','b','c','y','m','k')]
fig, axes = plt.subplots(2,2)
((ax1, ax2), (ax3, ax4)) = axes # unpack the axes
col = collections.LineCollection([spiral], offsets=xyo,
transOffset=ax1.transData)
trans = fig.dpi_scale_trans + transforms.Affine2D().scale(1.0/72.0)
col.set_transform(trans) # the points to pixels transform
# Note: the first argument to the collection initializer
# must be a list of sequences of x,y tuples; we have only
# one sequence, but we still have to put it in a list.
ax1.add_collection(col, autolim=True)
# autolim=True enables autoscaling. For collections with
# offsets like this, it is neither efficient nor accurate,
# but it is good enough to generate a plot that you can use
# as a starting point. If you know beforehand the range of
# x and y that you want to show, it is better to set them
# explicitly, leave out the autolim kwarg (or set it to False),
# and omit the 'ax1.autoscale_view()' call below.
# Make a transform for the line segments such that their size is
# given in points:
col.set_color(colors)
ax1.autoscale_view() # See comment above, after ax1.add_collection.
ax1.set_title('LineCollection using offsets')
# The same data as above, but fill the curves.
col = collections.PolyCollection([spiral], offsets=xyo,
transOffset=ax2.transData)
trans = transforms.Affine2D().scale(fig.dpi/72.0)
col.set_transform(trans) # the points to pixels transform
ax2.add_collection(col, autolim=True)
col.set_color(colors)
ax2.autoscale_view()
ax2.set_title('PolyCollection using offsets')
# 7-sided regular polygons
col = collections.RegularPolyCollection(7,
sizes = np.fabs(xx)*10.0, offsets=xyo,
transOffset=ax3.transData)
trans = transforms.Affine2D().scale(fig.dpi/72.0)
col.set_transform(trans) # the points to pixels transform
ax3.add_collection(col, autolim=True)
col.set_color(colors)
ax3.autoscale_view()
ax3.set_title('RegularPolyCollection using offsets')
# Simulate a series of ocean current profiles, successively
# offset by 0.1 m/s so that they form what is sometimes called
# a "waterfall" plot or a "stagger" plot.
nverts = 60
ncurves = 20
offs = (0.1, 0.0)
yy = np.linspace(0, 2*np.pi, nverts)
ym = np.amax(yy)
xx = (0.2 + (ym-yy)/ym)**2 * np.cos(yy-0.4) * 0.5
segs = []
for i in range(ncurves):
xxx = xx + 0.02*rs.randn(nverts)
curve = list(zip(xxx, yy*100))
segs.append(curve)
col = collections.LineCollection(segs, offsets=offs)
ax4.add_collection(col, autolim=True)
col.set_color(colors)
ax4.autoscale_view()
ax4.set_title('Successive data offsets')
ax4.set_xlabel('Zonal velocity component (m/s)')
ax4.set_ylabel('Depth (m)')
# Reverse the y-axis so depth increases downward
ax4.set_ylim(ax4.get_ylim()[::-1])
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