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I am trying to plot circles in matplotlib, but the outcome is always an empty plot.
E.g.
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as mpatches
import matplotlib.collections as mcollections
fig = plt.figure()
fig.set_size_inches(18.5, 10.5, forward=True)
ax = fig.add_subplot(111, aspect='equal')
x = np.array([17., 29., 41., 3., 15.])
y = np.array([21., 41., 30., 19., 5.])
r = np.array([22.8035085, 46.04345773, 46.61544808, 16., 12.16552506])
patches = [mpatches.Circle((xx, yy), rr) for xx, yy, rr in zip(x, y, r)]
collection = mcollections.PatchCollection(patches)
ax.add_collection(collection)
fig.savefig("test.png")
This produces an empty plot, the same when I try with add_artist. Hopefully someone can point me to where I am going wrong! Thank you
962
It means if we are not using the show() function, it wouldn't show any plot. When we use the show() function in the non-interactive mode. That means when we write the code in the file it will show all the figures or plots and blocks until the plots have been closed.
In the current versions of the IPython notebook and jupyter notebook, it is not necessary to use the %matplotlib inline function. As, whether you call matplotlib. pyplot. show() function or not, the graph output will be displayed in any case.
Saving a plot on your disk as an image file Now if you want to save matplotlib figures as image files programmatically, then all you need is matplotlib. pyplot. savefig() function. Simply pass the desired filename (and even location) and the figure will be stored on your disk.
The reason your plot is blank is that matplotlib didn't auto-adjust the axis according to the range of your patches. Usually, it will do the auto-adjust jobs with some main plot functions, such as plt.plot (), plt.scatter () .... As far as I'm concerned, it's not designed for drawing geometric figures like triangles, rectangle and circles.
The title of the figure is ‘matplotlib.figure.Figure.clear () function Example’. The gridlines are also plotted for the figure by setting ax.grid (True). But before the plt.show () statement that shows the plotted figure, we use the fig.clear () function. The fig.clear () function clears the figure plot when ‘True’ is an argument.
Matplotlib is a library in Python, which is a numerical – mathematical extension for NumPy library. The figure module of the Matplotlib library provides the top-level Artist, the Figure, which contains all the plot elements. The figure module is used to control the subplots’ default spacing and top-level container for all plot elements.
The ‘keep_observers’ parameter in figure.clear() function is a boolean value. Return type The clear() function does not return any value. It is used in python programs to clear plots. Example of Matplotlib Figure clear plot
In addition to the other answer provided, you can use ax.autoscale() before saving the plot. that will result in
125
Your problem here is not the paches haven't been drawed. The reason your plot is blank is that matplotlib didn't auto-adjust the axis according to the range of your patches.
Usually, it will do the auto-adjust jobs with some main plot functions, such as plt.plot(), plt.scatter() .... As far as I'm concerned, it's not designed for drawing geometric figures like triangles, rectangle and circles. This may also explain why this called patches in matplotlib.
So what you need to do is to specify the range of the axis manully by using something like this in your case:
plt.axis([-50, 100, -50, 100])
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