"""
Examples used in talks
:githublink:`%|py|5`
"""
[docs]def example_networkx(ax=None, **options):
"""
Example using :epkg:`networkx`.
:param ax: axis
:param options: look at the code
:return: ax
:githublink:`%|py|14`
"""
import networkx as nx
import matplotlib.pyplot as plt
G = nx.random_geometric_graph(200, 0.125)
# position is stored as node attribute data for random_geometric_graph
pos = nx.get_node_attributes(G, 'pos')
# find node near center (0.5,0.5)
dmin = 1
ncenter = 0
for n in pos:
x, y = pos[n]
d = (x - 0.5) ** 2 + (y - 0.5) ** 2
if d < dmin:
ncenter = n
dmin = d
# color by path length from node near center
p = nx.single_source_shortest_path_length(G, ncenter)
if ax is None:
_, ax = plt.subplots(
nrows=1, ncols=1, figsize=options.get('figsize', (5, 5)))
nx.draw_networkx_edges(G, pos, nodelist=[ncenter], alpha=0.4, ax=ax)
nx.draw_networkx_nodes(G, pos, nodelist=p.keys(),
node_size=80, ax=ax)
ax.set_xlim(-0.05, 1.05)
ax.set_ylim(-0.05, 1.05)
ax.axis('off')
return ax
[docs]def example_confidence_interval(ax=None, seaborn=False, **options):
"""
Draws pseudo confidence interval for a regression
in a :epkg:`matplotlib` graph.
:param ax: axis
:param seaborn: uses :epkg:`seaborn`
instead of :epkg:`matplotlib`
:param options: look at the code
:return: ax
:githublink:`%|py|59`
"""
import matplotlib.pyplot as plt
if ax is None:
_, ax = plt.subplots(
nrows=1, ncols=1, figsize=options.get('figsize', (5, 5)))
import scipy
import numpy
nx, nboot = 22, 400
x = scipy.linspace(0.0, 1.0, nx) # pylint: disable=E1101
data = x + numpy.random.normal(loc=0.0, scale=0.1, size=nx)
yp = scipy.polyfit(x, data, 1) # pylint: disable=E1101
y = scipy.polyval(yp, x) # pylint: disable=E1101
if seaborn:
from seaborn import regplot
return regplot(x=x, y=y, ax=ax)
else:
r = data - y
for _ in range(nboot):
pc = scipy.polyfit( # pylint: disable=E1101
x, y + r[scipy.random.randint(0, nx - 1, nx)], 1) # pylint: disable=E1101
ax.plot(x, scipy.polyval(pc, x), 'k-', # pylint: disable=E1101
linewidth=2, alpha=3.0 / float(nboot))
ax.plot(x, y, 'k-')
ax.plot(x, data, 'ko')
return ax
[docs]def example_cartopy(ax=None, **options):
"""
Draws a map of France
with :epkg:`cartopy`.
:param ax: axis
:param options: look at the code
:return: ax
:githublink:`%|py|97`
"""
import cartopy.crs as ccrs
import cartopy.feature as cfeature
import matplotlib.pyplot as plt
fig = plt.figure(figsize=(7, 7))
ax = fig.add_subplot(1, 1, 1, projection=ccrs.PlateCarree())
ax.set_extent([-5, 10, 42, 52])
ax.add_feature(cfeature.OCEAN)
ax.add_feature(cfeature.COASTLINE)
ax.add_feature(cfeature.RIVERS)
ax.add_feature(cfeature.LAKES)
ax.add_feature(cfeature.LAND)
ax.add_feature(cfeature.BORDERS, linestyle=':')
ax.plot([2.35, 2.20], [48.85, 48.71], '.')
ax.text(2.35, 48.85, "Paris")
ax.text(2.20, 48.71, "Saclay", ha="right")
ax.set_title('France')
return ax
[docs]def example_pydy(ax=None, **options):
"""
Example from the documentation of
:epkg:`pydy`.
:param ax: matplotlib axis
@parm options extra options
:return: ax
:githublink:`%|py|127`
"""
# part 1
from sympy import symbols
import sympy.physics.mechanics as me
mass, stiffness, damping, gravity = symbols('m, k, c, g')
position, speed = me.dynamicsymbols('x v')
positiond = me.dynamicsymbols('x', 1)
force = me.dynamicsymbols('F')
ceiling = me.ReferenceFrame('N')
origin = me.Point('origin')
origin.set_vel(ceiling, 0)
center = origin.locatenew('center', position * ceiling.x)
center.set_vel(ceiling, speed * ceiling.x)
block = me.Particle('block', center, mass)
kinematic_equations = [speed - positiond]
force_magnitude = mass * gravity - stiffness * position - damping * speed + force
forces = [(center, force_magnitude * ceiling.x)]
particles = [block]
kane = me.KanesMethod(ceiling, q_ind=[position], u_ind=[speed],
kd_eqs=kinematic_equations)
kane.kanes_equations(forces, particles)
# part 2
from numpy import linspace, sin
from pydy.system import System
sys = System(kane,
constants={mass: 1.0, stiffness: 1.0,
damping: 0.2, gravity: 9.8},
specifieds={force: lambda x, t: sin(t)},
initial_conditions={position: 0.1, speed: -1.0},
times=linspace(0.0, 10.0, 1000))
y = sys.integrate()
# part 3
import matplotlib.pyplot as plt
if ax is None:
_, ax = plt.subplots(
nrows=1, ncols=1, figsize=options.get('figsize', (5, 5)))
ax.plot(sys.times, y)
ax.legend((str(position), str(speed)))
return ax