Develop Reference

Wrong matplotlib animation

I have the following code that should draw a cycloid with animation and save it to a gif
but after running the program, a white square appears that covers everything, I can't find the reason cycloid_animation
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation
from matplotlib.animation import FuncAnimation, PillowWriter
plt.rcParams['animation.html'] = 'html5'
R = 1
def circle(a, b, r):
# (a,b): the center of the circle
# r: the radius of the circle
# T: The number of the segments
T = 100
x, y = [0]*T, [0]*T
for i,theta in enumerate(np.linspace(0,2*np.pi,T)):
x[i] = a + r*np.cos(theta)
y[i] = b + r*np.sin(theta)
return x, y
# Calculate the cycloid line
thetas = np.linspace(0,4*np.pi,100)
cycloid_x = R*(thetas-np.sin(thetas))
cycloid_y = R*(1-np.cos(thetas))
cycloid_c = R*thetas
fig = plt.figure()
lns = []
trans = plt.axes().transAxes
for i in range(len(thetas)):
x,y = circle(cycloid_c[i], R, R)
ln1, = plt.plot(x, y, 'g-', lw=2)
ln2, = plt.plot(cycloid_x[:i+1] ,cycloid_y[:i+1], 'r-', lw=2)
ln3, = plt.plot(cycloid_x[i], cycloid_y[i], 'bo', markersize=4)
ln4, = plt.plot([cycloid_c[i], cycloid_x[i]], [R,cycloid_y[i]], 'y-', lw=2)
tx1 = plt.text(0.05, 0.8, r'$\theta$ = %.2f $\pi$' % (thetas[i]/np.pi), transform=trans)
lns.append([ln1,ln2,ln3,ln4,tx1])
plt.xlim(0,15)
plt.ylim(0,3)
plt.xlabel('x')
plt.ylabel('y')
plt.grid()
plt.axes().set_aspect('equal')
ani = animation.ArtistAnimation(fig, lns, interval=50)
#ani.save('cycloid_ArtistAnimation.mp4',writer='ffmpeg')
ani.save('cycloid_ArtistAnimation.gif',writer='pillow')
ani

Each time you call plt.axis() you are creating a new axis on top of the figure. Since what you want is to get the current axis and then apply the transformations, after creating the figure you should call plt.gca() to get the current axis and use that instead.
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation
from matplotlib.animation import FuncAnimation, PillowWriter
plt.rcParams['animation.html'] = 'html5'
R = 1
def circle(a, b, r):
# (a,b): the center of the circle
# r: the radius of the circle
# T: The number of the segments
T = 100
x, y = [0]*T, [0]*T
for i,theta in enumerate(np.linspace(0,2*np.pi,T)):
x[i] = a + r*np.cos(theta)
y[i] = b + r*np.sin(theta)
return x, y
# Calculate the cycloid line
thetas = np.linspace(0,4*np.pi,100)
cycloid_x = R*(thetas-np.sin(thetas))
cycloid_y = R*(1-np.cos(thetas))
cycloid_c = R*thetas
fig = plt.figure()
lns = []
trans = plt.gca().transAxes #<=== HERE
for i in range(len(thetas)):
x,y = circle(cycloid_c[i], R, R)
ln1, = plt.plot(x, y, 'g-', lw=2)
ln2, = plt.plot(cycloid_x[:i+1] ,cycloid_y[:i+1], 'r-', lw=2)
ln3, = plt.plot(cycloid_x[i], cycloid_y[i], 'bo', markersize=4)
ln4, = plt.plot([cycloid_c[i], cycloid_x[i]], [R,cycloid_y[i]], 'y-', lw=2)
tx1 = plt.text(0.05, 0.8, r'$\theta$ = %.2f $\pi$' % (thetas[i]/np.pi), transform=trans)
lns.append([ln1,ln2,ln3,ln4,tx1])
plt.xlim(0,15)
plt.ylim(0,3)
plt.xlabel('x')
plt.ylabel('y')
plt.grid()
plt.gca().set_aspect('equal') #<=== And HERE
ani = animation.ArtistAnimation(fig, lns, interval=50)
#ani.save('cycloid_ArtistAnimation.mp4',writer='ffmpeg')
ani.save('cycloid_ArtistAnimation.gif',writer='pillow')

Scope in Python subplot similar to MATLAB's stackedplot()

Is there a plot function available in Python that is same as MATLAB's stackedplot()?
stackedplot() in MATLAB can line plot several variables with the same X axis and are stacked vertically. Additionally, there is a scope in this plot that shows the value of all variables for a given X just by moving the cursor (please see the attached plot). I have been able to generate stacked subplots in Python with no issues, however, not able to add a scope like this that shows the value of all variables by moving the cursor. Is this feature available in Python?
This is a plot using MATLAB's stackedplot():
import pandas as pd
import numpy as np
from datetime import datetime, date, time
import matplotlib.pyplot as plt
import matplotlib
import matplotlib.transforms as transforms
import mplcursors
from collections import Counter
import collections
def flatten(x):
result = []
for el in x:
if isinstance(x, collections.Iterable) and not isinstance(el, str):
result.extend(flatten(el))
else:
result.append(el)
return result
def shared_scope(sel):
sel.annotation.set_visible(False) # hide the default annotation created by mplcursors
x = sel.target[0]
for ax in axes:
for plot in plotStore:
da = plot.get_ydata()
if type(da[0]) is np.datetime64: #pd.Timestamp
yData = matplotlib.dates.date2num(da) # to numerical values
vals = np.interp(x, plot.get_xdata(), yData)
dates = matplotlib.dates.num2date(vals) # to matplotlib dates
y = datetime.strftime(dates,'%Y-%m-%d %H:%M:%S') # to strings
annot = ax.annotate(f'{y:.30s}', (x, vals), xytext=(15, 10), textcoords='offset points',
bbox=dict(facecolor='tomato', edgecolor='black', boxstyle='round', alpha=0.5))
sel.extras.append(annot)
else:
y = np.interp(x, plot.get_xdata(), plot.get_ydata())
annot = ax.annotate(f'{y:.2f}', (x, y), xytext=(15, 10), textcoords='offset points', arrowprops=dict(arrowstyle="->",connectionstyle="angle,angleA=0,angleB=90,rad=10"),
bbox=dict(facecolor='tomato', edgecolor='black', boxstyle='round', alpha=0.5))
sel.extras.append(annot)
vline = ax.axvline(x, color='k', ls=':')
sel.extras.append(vline)
trans = transforms.blended_transform_factory(axes[0].transData, axes[0].transAxes)
text1 = axes[0].text(x, 1.01, f'{x:.2f}', ha='center', va='bottom', color='blue', clip_on=False, transform=trans)
sel.extras.append(text1)
# Data to plot
data = pd.DataFrame(columns = ['timeOfSample','Var1','Var2'])
data.timeOfSample = ['2020-05-10 09:09:02','2020-05-10 09:09:39','2020-05-10 09:40:07','2020-05-10 09:40:45','2020-05-12 09:50:45']
data['timeOfSample'] = pd.to_datetime(data['timeOfSample'])
data.Var1 = [10,50,100,5,25]
data.Var2 = [20,55,70,60,50]
variables = ['timeOfSample',['Var1','Var2']] # variables to plot - Var1 and Var2 to share a plot
nPlot = len(variables)
dataPts = np.arange(0, len(data[variables[0]]), 1) # x values for plots
plotStore = [0]*len(flatten(variables)) # to store all the plots for annotation purposes later
fig, axes = plt.subplots(nPlot,1,sharex=True)
k=0
for i in range(nPlot):
if np.size(variables[i])==1:
yData = data[variables[i]]
line, = axes[i].plot(dataPts,yData,label = variables[i])
plotStore[k]=line
k = k+1
else:
for j in range(np.size(variables[i])):
yData = data[variables[i][j]]
line, = axes[i].plot(dataPts,yData,label = variables[i][j])
plotStore[k]=line
k = k+1
axes[i].set_ylabel(variables[i])
cursor = mplcursors.cursor(plotStore, hover=True)
cursor.connect('add', shared_scope)
plt.xlabel('Samples')
plt.show()

mplcursors can be used to create annotations while hovering, moving texts and vertical bars. sel.extras.append(...) helps to automatically hide the elements that aren't needed anymore.
import matplotlib.pyplot as plt
import matplotlib.transforms as transforms
import mplcursors
import numpy as np
def shared_scope(sel):
x = sel.target[0]
annotation_text = f'x: {x:.2f}'
for ax, plot in zip(axes, all_plots):
y = np.interp(x, plot.get_xdata(), plot.get_ydata())
annotation_text += f'\n{plot.get_label()}: {y:.2f}'
vline = ax.axvline(x, color='k', ls=':')
sel.extras.append(vline)
sel.annotation.set_text(annotation_text)
trans = transforms.blended_transform_factory(axes[0].transData, axes[0].transAxes)
text1 = axes[0].text(x, 1.01, f'{x:.2f}', ha='center', va='bottom', color='blue', clip_on=False, transform=trans)
sel.extras.append(text1)
fig, axes = plt.subplots(figsize=(15, 10), nrows=3, sharex=True)
y1 = np.random.uniform(-1, 1, 100).cumsum()
y2 = np.random.uniform(-1, 1, 100).cumsum()
y3 = np.random.uniform(-1, 1, 100).cumsum()
all_y = [y1, y2, y3]
all_labels = ['Var1', 'Var2', 'Var3']
all_plots = [ax.plot(y, label=label)[0]
for ax, y, label in zip(axes, all_y, all_labels)]
for ax, label in zip(axes, all_labels):
ax.set_ylabel(label)
cursor = mplcursors.cursor(all_plots, hover=True)
cursor.connect('add', shared_scope)
plt.show()
Here is a version with separate annotations per subplot:
import matplotlib.pyplot as plt
import matplotlib.transforms as transforms
import mplcursors
import numpy as np
def shared_scope(sel):
sel.annotation.set_visible(False) # hide the default annotation created by mplcursors
x = sel.target[0]
for ax, plot in zip(axes, all_plots):
y = np.interp(x, plot.get_xdata(), plot.get_ydata())
vline = ax.axvline(x, color='k', ls=':')
sel.extras.append(vline)
annot = ax.annotate(f'{y:.2f}', (x, y), xytext=(5, 0), textcoords='offset points',
bbox=dict(facecolor='tomato', edgecolor='black', boxstyle='round', alpha=0.5))
sel.extras.append(annot)
trans = transforms.blended_transform_factory(axes[0].transData, axes[0].transAxes)
text1 = axes[0].text(x, 1.01, f'{x:.2f}', ha='center', va='bottom', color='blue', clip_on=False, transform=trans)
sel.extras.append(text1)
fig, axes = plt.subplots(figsize=(15, 10), nrows=3, sharex=True)
y1 = np.random.uniform(-1, 1, 100).cumsum()
y2 = np.random.uniform(-1, 1, 100).cumsum()
y3 = np.random.uniform(-1, 1, 100).cumsum()
all_y = [y1, y2, y3]
all_labels = ['Var1', 'Var2', 'Var3']
all_plots = [ax.plot(y, label=label)[0]
for ax, y, label in zip(axes, all_y, all_labels)]
for ax, label in zip(axes, all_labels):
ax.set_ylabel(label)
cursor = mplcursors.cursor(all_plots, hover=True)
cursor.connect('add', shared_scope)
plt.show()

matplotlib.widgets.Slider with fill_between

I'm trying to Add the slider in the plot similar to the slider demo example.
I'm plotting fill_between which gives PolyCollection object.
Although I tried with plot too which give Line2D object as shown picture below, but plot doesn't update as expected as in demo.
code
import numpy as np
import scipy.stats as ss
import matplotlib.pyplot as plt
import matplotlib.widgets as widgets
def get_pdf(mu, sigma=1, offset=4):
o = sigma * offset
x = np.linspace(mu - o, mu + o, 100)
rv = ss.norm(mu, sigma)
return x, rv.pdf(x)
fig, ax = plt.subplots()
plt.subplots_adjust(bottom=0.25)
ax.fill_between(*get_pdf(0, 1), alpha=0.7)
# t = plt.fill_between(*get_pdf(2, 1), alpha=0.7) # this gives ployCollection
t = ax.plot(*get_pdf(2, 1), label='treatment', alpha=0.7)
a = plt.axes([0.25, 0.1, 0.5, 0.03])
slider = widgets.Slider(a, "shift", 0, 10, valinit=2, valstep=1)
def update(val):
x, y = get_pdf(val)
t[0].set_ydata(y)
fig.canvas.draw_idle()
slider.on_changed(update)
plt.show()

To update the line plot, t[0].set_xdata(x) needs to be set, as it is different for each call. In this particular case, get_pdf each time returns the same y.
Updating the coordinates of the polyCollection generated by fill_between doesn't seem to be possible. However, you can delete and recreate it at every update. Note that this is slower than just updating the coordinates.
import numpy as np
import scipy.stats as ss
import matplotlib.pyplot as plt
import matplotlib.widgets as widgets
def get_pdf(mu, sigma=1, offset=4):
o = sigma * offset
x = np.linspace(mu - o, mu + o, 100)
rv = ss.norm(mu, sigma)
return x, rv.pdf(x)
fig, ax = plt.subplots()
plt.subplots_adjust(bottom=0.25)
ax.fill_between(*get_pdf(0, 1), alpha=0.7)
t = ax.fill_between(*get_pdf(2), color='crimson', alpha=0.7)
a = plt.axes([0.25, 0.1, 0.5, 0.03])
slider = widgets.Slider(a, "shift", 0, 10, valinit=2, valstep=1)
def update(val):
global t
t.remove()
t = ax.fill_between(*get_pdf(val), color='crimson', alpha=0.7)
fig.canvas.draw_idle()
slider.on_changed(update)
plt.show()

Animate a segment in a 3d space

I got a .dat file which contains the coordinates of a segment in 3d space.
The file has several lines, each single line characterizes the position at a particular time.
I tried this code:
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation
from mpl_toolkits.mplot3d import Axes3D
dati = np.loadtxt('dati.dat')
t=0
p1=[dati[t,1],dati[t,2],dati[t,3]]
p2=[dati[t,4],dati[t,5],dati[t,6]]
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
seg,=ax.plot(p1,p2)
def updateFigure(t,dati,seg):
p1=[dati[t,1],dati[t,2],dati[t,3]]
p2=[dati[t,4],dati[t,5],dati[t,6]]
seg.set_data(p1,p2)
return seg,
ani=animation.FuncAnimation(fig, updateFigure,iMax, fargs=(dati,seg), interval=100, blit=True)
plt.show()
The program doesn't report errors but the figure doesn't move.
The same code, a bit modified, in the 2d space works..

Instead of calling set_data, you could set seg._verts3d directly, though note that manipulating the private variable _verts3d is relying on an implementation detail, not part of the Line3D public interface:
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.animation as animation
from mpl_toolkits.mplot3d import Axes3D
iMax = N = 500
theta = np.linspace(0, 6*np.pi, N)
x = np.cos(theta)
y = np.sin(theta)
z = np.linspace(0, 1, N)
step = 10
dati = np.column_stack(
[theta, x, np.roll(x, -step), np.roll(x, -2*step)
, y, np.roll(y, -step), np.roll(y, -2*step)
, z, np.roll(z, -step), np.roll(z, -2*step)])
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
seg, = plt.plot([], [])
ax.set_xlim3d(-1, 1)
ax.set_ylim3d(-1, 1)
ax.set_zlim3d(0, 1)
def init():
return seg,
def updateFigure(t):
p1 = dati[t, 1:4]
p2 = dati[t, 4:7]
p3 = dati[t, 7:10]
seg._verts3d = (p1, p2, p3)
return seg,
ani = animation.FuncAnimation(
fig, updateFigure
, init_func=init
, frames=iMax
, interval=5, blit=True)
plt.show()

Adding errorbars to 3D plot in matplotlib

I can't find a way to draw errorbars in a 3D scatter plot in matplotlib.
Basically, for the following piece of code
from mpl_toolkits.mplot3d import axes3d
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
X, Y, Z = axes3d.get_test_data(1)
ax.scatter(X, Y, zs = Z, zdir = 'z')
I am looking for something like
ax.errorbar(X,Y, zs = Z, dY, dX, zserr = dZ)
Is there a way to do this in mplot3d? If not, are there other libraries with this function?

There is clearly example on forum http://mple.m-artwork.eu/home/posts/simple3dplotwith3derrorbars
Here is the code but is not built-in functionality:
import numpy as np
import matplotlib.pyplot as plt
import mpl_toolkits.mplot3d.axes3d as axes3d
fig = plt.figure(dpi=100)
ax = fig.add_subplot(111, projection='3d')
#data
fx = [0.673574075,0.727952994,0.6746285]
fy = [0.331657721,0.447817839,0.37733386]
fz = [18.13629648,8.620699842,9.807536512]
#error data
xerror = [0.041504064,0.02402152,0.059383144]
yerror = [0.015649804,0.12643117,0.068676131]
zerror = [3.677693713,1.345712547,0.724095592]
#plot points
ax.plot(fx, fy, fz, linestyle="None", marker="o")
#plot errorbars
for i in np.arange(0, len(fx)):
ax.plot([fx[i]+xerror[i], fx[i]-xerror[i]], [fy[i], fy[i]], [fz[i], fz[i]], marker="_")
ax.plot([fx[i], fx[i]], [fy[i]+yerror[i], fy[i]-yerror[i]], [fz[i], fz[i]], marker="_")
ax.plot([fx[i], fx[i]], [fy[i], fy[i]], [fz[i]+zerror[i], fz[i]-zerror[i]], marker="_")
#configure axes
ax.set_xlim3d(0.55, 0.8)
ax.set_ylim3d(0.2, 0.5)
ax.set_zlim3d(8, 19)
plt.show()

I ended up writing the method for matplotlib: official example for 3D errorbars:
import matplotlib.pyplot as plt
import numpy as np
ax = plt.figure().add_subplot(projection='3d')
# setting up a parametric curve
t = np.arange(0, 2*np.pi+.1, 0.01)
x, y, z = np.sin(t), np.cos(3*t), np.sin(5*t)
estep = 15
i = np.arange(t.size)
zuplims = (i % estep == 0) & (i // estep % 3 == 0)
zlolims = (i % estep == 0) & (i // estep % 3 == 2)
ax.errorbar(x, y, z, 0.2, zuplims=zuplims, zlolims=zlolims, errorevery=estep)
ax.set_xlabel("X label")
ax.set_ylabel("Y label")
ax.set_zlabel("Z label")
plt.show()