I'm just starting using Matplotlib the "right" way. I'm writing various programs that will each give me back a time series, and I'm looking to superimpose the graphs of the various time series, like this:
I think what I want is a single Axes instance defined in the main function, then I call each of my little functions, and they all return a Line2D instance, and then I'll put them all on the Axes object I created.
But I'm having trouble taking an existing Line2D object and adding it to an existing Axes object (like I'd want to do with the output of my function.) I thought of taking a Line2D called a and say ax.add_line(a).
import matplotlib.pyplot as plt
a, = plt.plot([1,2,3], [3,4,5], label = 'a')
fig, ax = plt.subplots()
ax.add_line(a)
Gives me a RuntimeError: "Can not put single artist in more than one figure."
I'm guessing that over time Matplotlib has stopped wanting users to be able to add a given line to any Axes they want. A similar thing is discussed in the comments of this answer, except there they're talking about an Axes object in two different Figure objects.
What's the best way to accomplish what I want? I'd rather keep my main script tidy, and not say ax.plot(some_data) over and over when I want to superimpose these lines.
Indeed, you cannot add the same artist to more than one axes or figure.
But for what I understand from your question, that isn't really necessary.
So let's just do as you propose;
"I thought of taking a Line2D called a and say ax.add_line(a)."
import numpy as np
import matplotlib.pyplot as plt
def get_line(label="a"):
return plt.Line2D(np.linspace(0,1,10), np.random.rand(10), label = label)
fig, ax = plt.subplots()
ax.add_line(get_line(label="a"))
ax.add_line(get_line(label="b"))
ax.add_line(get_line(label="z"))
ax.legend()
plt.show()
The way matplotlib would recommend is to create functions that take an axes as input and plot to that axes.
import numpy as np
import matplotlib.pyplot as plt
def plot_line(ax=None, label="a"):
ax = ax or plt.gca()
line, = ax.plot(np.linspace(0,1,10), np.random.rand(10), label = label)
return line
fig, ax = plt.subplots()
plot_line(ax, label="a")
plot_line(ax, label="b")
plot_line(ax, label="z")
ax.legend()
plt.show()
A possible work around for your problem:
import matplotlib.pyplot as plt
x = np.array([1,2,3])
y = np.array([3,4,5])
label = '1'
def plot(x,y,label):
a, = plt.plot(x,y, label = label)
return a
fig, ax = plt.subplots()
plot(x,y,label)
plot(x,1.5*y,label)
You can put your plot command now in a loop with changing labels. You can still use the ax handle to modify/define the plot parameters.
Related
I'm trying to share two subplots axes, but I need to share the x axis after the figure was created. E.g. I create this figure:
import numpy as np
import matplotlib.pyplot as plt
t = np.arange(1000)/100.
x = np.sin(2*np.pi*10*t)
y = np.cos(2*np.pi*10*t)
fig = plt.figure()
ax1 = plt.subplot(211)
plt.plot(t,x)
ax2 = plt.subplot(212)
plt.plot(t,y)
# some code to share both x axes
plt.show()
Instead of the comment I want to insert some code to share both x axes.
How do I do this? There are some relevant sounding attributes
_shared_x_axes and _shared_x_axes when I check to figure axis (fig.get_axes()) but I don't know how to link them.
The usual way to share axes is to create the shared properties at creation. Either
fig=plt.figure()
ax1 = plt.subplot(211)
ax2 = plt.subplot(212, sharex = ax1)
or
fig, (ax1, ax2) = plt.subplots(nrows=2, sharex=True)
Sharing the axes after they have been created should therefore not be necessary.
However if for any reason, you need to share axes after they have been created (actually, using a different library which creates some subplots, like here might be a reason), there would still be a solution:
Using
ax1.get_shared_x_axes().join(ax1, ax2)
creates a link between the two axes, ax1 and ax2. In contrast to the sharing at creation time, you will have to set the xticklabels off manually for one of the axes (in case that is wanted).
A complete example:
import numpy as np
import matplotlib.pyplot as plt
t= np.arange(1000)/100.
x = np.sin(2*np.pi*10*t)
y = np.cos(2*np.pi*10*t)
fig=plt.figure()
ax1 = plt.subplot(211)
ax2 = plt.subplot(212)
ax1.plot(t,x)
ax2.plot(t,y)
ax1.get_shared_x_axes().join(ax1, ax2)
ax1.set_xticklabels([])
# ax2.autoscale() ## call autoscale if needed
plt.show()
The other answer has code for dealing with a list of axes:
axes[0].get_shared_x_axes().join(axes[0], *axes[1:])
As of Matplotlib v3.3 there now exist Axes.sharex, Axes.sharey methods:
ax1.sharex(ax2)
ax1.sharey(ax3)
Just to add to ImportanceOfBeingErnest's answer above:
If you have an entire list of axes objects, you can pass them all at once and have their axes shared by unpacking the list like so:
ax_list = [ax1, ax2, ... axn] #< your axes objects
ax_list[0].get_shared_x_axes().join(ax_list[0], *ax_list)
The above will link all of them together. Of course, you can get creative and sub-set your list to link only some of them.
Note:
In order to have all axes linked together, you do have to include the first element of the axes_list in the call, despite the fact that you are invoking .get_shared_x_axes() on the first element to start with!
So doing this, which would certainly appear logical:
ax_list[0].get_shared_x_axes().join(ax_list[0], *ax_list[1:])
... will result in linking all axes objects together except the first one, which will remain entirely independent from the others.
I'm trying to share two subplots axes, but I need to share the x axis after the figure was created. E.g. I create this figure:
import numpy as np
import matplotlib.pyplot as plt
t = np.arange(1000)/100.
x = np.sin(2*np.pi*10*t)
y = np.cos(2*np.pi*10*t)
fig = plt.figure()
ax1 = plt.subplot(211)
plt.plot(t,x)
ax2 = plt.subplot(212)
plt.plot(t,y)
# some code to share both x axes
plt.show()
Instead of the comment I want to insert some code to share both x axes.
How do I do this? There are some relevant sounding attributes
_shared_x_axes and _shared_x_axes when I check to figure axis (fig.get_axes()) but I don't know how to link them.
The usual way to share axes is to create the shared properties at creation. Either
fig=plt.figure()
ax1 = plt.subplot(211)
ax2 = plt.subplot(212, sharex = ax1)
or
fig, (ax1, ax2) = plt.subplots(nrows=2, sharex=True)
Sharing the axes after they have been created should therefore not be necessary.
However if for any reason, you need to share axes after they have been created (actually, using a different library which creates some subplots, like here might be a reason), there would still be a solution:
Using
ax1.get_shared_x_axes().join(ax1, ax2)
creates a link between the two axes, ax1 and ax2. In contrast to the sharing at creation time, you will have to set the xticklabels off manually for one of the axes (in case that is wanted).
A complete example:
import numpy as np
import matplotlib.pyplot as plt
t= np.arange(1000)/100.
x = np.sin(2*np.pi*10*t)
y = np.cos(2*np.pi*10*t)
fig=plt.figure()
ax1 = plt.subplot(211)
ax2 = plt.subplot(212)
ax1.plot(t,x)
ax2.plot(t,y)
ax1.get_shared_x_axes().join(ax1, ax2)
ax1.set_xticklabels([])
# ax2.autoscale() ## call autoscale if needed
plt.show()
The other answer has code for dealing with a list of axes:
axes[0].get_shared_x_axes().join(axes[0], *axes[1:])
As of Matplotlib v3.3 there now exist Axes.sharex, Axes.sharey methods:
ax1.sharex(ax2)
ax1.sharey(ax3)
Just to add to ImportanceOfBeingErnest's answer above:
If you have an entire list of axes objects, you can pass them all at once and have their axes shared by unpacking the list like so:
ax_list = [ax1, ax2, ... axn] #< your axes objects
ax_list[0].get_shared_x_axes().join(ax_list[0], *ax_list)
The above will link all of them together. Of course, you can get creative and sub-set your list to link only some of them.
Note:
In order to have all axes linked together, you do have to include the first element of the axes_list in the call, despite the fact that you are invoking .get_shared_x_axes() on the first element to start with!
So doing this, which would certainly appear logical:
ax_list[0].get_shared_x_axes().join(ax_list[0], *ax_list[1:])
... will result in linking all axes objects together except the first one, which will remain entirely independent from the others.
Due to the 2nd answer of this question I supposed the following code
import matplotlib.pyplot as plt
for i1 in range(2):
plt.figure(1)
f, ax = plt.subplots()
plt.plot((0,3), (2, 2), 'b')
for i2 in range(2):
plt.figure(2)
f, ax = plt.subplots()
plt.plot([1,2,3], [1,2,3], 'r')
plt.savefig('foo_{}_bar_{}.jpg'.format(i2, i1))
plt.close()
plt.figure(1)
plt.plot( [1,2,3],[1,2,3], 'r')
plt.savefig('bar_{}.jpg'.format(i1))
plt.close()
to create plots bar_0.jpg and bar_1.jpg showing a blue and a red line each.
However, figures look like
instead of
How can I achieve the desired behaviour?
Note that plots foo_*.jpg have to be closed and saved during handling of the bar plots.
You're already saving the Axes objects, so instead of calling the PyPlot plot function (which draws on the last created or activated Axes), use the objects' plot function:
ax.plot(...)
If you then give both a different name, say ax1 and ax2, you can draw on the one you like without interfering with the other. All plt. commands also exist as an Axes member function, but sometimes the name changes (plt.xticks becomes ax.set_xticks for example). See the documentation of Axes for details.
To save to figures, use the Figure objects in the same way:
f.savefig(...)
This API type is only just coming to Matlab, FYI, and will probably replace the old-fashioned "draw on the last active plot" behaviour in the future. The object-oriented approach here is more flexible with minimal overhead, so I strongly recommend you use it everywhere.
If unsure, better to make it explicit:
import matplotlib.pyplot as plt
for i1 in range(2):
fig1,ax1 = plt.subplots()
fig2,ax2 = plt.subplots()
ax1.plot([0,4],[2,2],'b')
for i2 in range(2):
ax2.plot([1,2,3],[1,2,3],'r')
fig2.savefig('abc{}.png'.format(2*i1+i2))
plt.figure(1)
ax1.plot([1,2,3],[1,2,3],'r')
fig1.savefig('cba{}.png'.format(i1))
K here's a more precise example of what I am trying to do. I am using WXBuilder for Python as my user interface with multiple plotting functionality i.e. the user must be able to plot a graph based on their chosen parameters. After a graph is plotted I want the user to be able to plot a second without closing the first figure. This is for comparison purposes. Below is an oversimplified example of what I am looking to do.
import matplotlib as plt
def OnPlotClick1(self, event):
plt.plot(self.DateArray1, self.kVAArray2)
plt.show()
def OnPlotClick2(self, event):
plt.plot(self.DateArray1, self.kVAArray2)
plt.show()
Now I am assuming my problem is arising due plotting and showing() the graph, and therefore the program somehow is blocked from functionality until the first figure or plot window is closed.
I hope this explains my problem better.
You should not block show. Use:
import matplotlib.pylab as plt
plt.plot([1,2,3]) # first plot
plt.show(block=False) # do not block
plt.plot([11,21,31]) # second plot
Each window is in matplotlib parlance, a new figure. You can call plt.subplots twice to create two figures:
import numpy as np
import matplotlib.pyplot as plt
x = np.linspace(0, 10, 1000)
y1 = np.sin(x)*np.exp(-x/5.0)
y2 = np.sin(x**2)*x
fig1, ax1 = plt.subplots()
ax1.plot(x, y1)
fig2, ax2 = plt.subplots()
ax2.plot(x, y2)
plt.show()
Note that plt.show() starts a GUI event loop and so generally it should only be called once per script.
You can also draw 2 or more than 2 plotters in the same figure
import matplotlib.pyplot as plt
def my_plotter(ax, data1, data2, param_dict):
out = ax.plot(data1, data2, **param_dict)
return out
fig, (ax1, ax2) = plt.subplots(1, 2)
#here you put your data
data1=[0,1,2,3,8]
data2=[0,1,2,3,8]
data3=[0,1,2,3,8]
data4=[0,1,2,3,8]
my_plotter(ax1, data1, data2, {'marker':'x'})
my_plotter(ax2, data3, data4, {'marker':'o'})
plt.show()
You can either follow #(Corrupted MyStack) suggestion or with interactive graphic devide. Run
plt.ion()
once, anytime before you start the plots. To turn it off
plt.ioff()
I am plotting and saving thousands of files for later animation in a loop like so:
import matplotlib.pyplot as plt
for result in results:
plt.figure()
plt.plot(result) # this changes
plt.xlabel('xlabel') # this doesn't change
plt.ylabel('ylabel') # this doesn't change
plt.title('title') # this changes
plt.ylim([0,1]) # this doesn't change
plt.grid(True) # this doesn't change
plt.savefig(location, bbox_inches=0) # this changes
When I run this with a lot of results, it crashes after several thousand plots are saved. I think what I want to do is reuse my axes like in this answer: https://stackoverflow.com/a/11688881/354979 but I don't understand how. How can I optimize it?
I would create a single figure and clear the figure each time (use .clf).
import matplotlib.pyplot as plt
fig = plt.figure()
for result in results:
fig.clf() # Clears the current figure
...
You are running out of memory since each call to plt.figure creates a new figure object. Per #tcaswell's comment, I think this would be faster than .close. The differences are explained in:
When to use cla(), clf() or close() for clearing a plot in matplotlib?
Although this question is old, the answer would be:
import matplotlib.pyplot as plt
fig = plt.figure()
plot = plt.plot(results[0])
title = plt.title('title')
plt.xlabel('xlabel')
plt.ylabel('ylabel')
plt.ylim([0,1])
plt.grid(True)
for i in range(1,len(results)):
plot.set_data(results[i])
title.set_text('new title')
plt.savefig(location[i], bbox_inches=0)
plt.close('all')