[Matplotlib-users] selecting points inside plot

[Jody Klymak]

Hi Jean-Philippe,

Just to explicitly implement Ben’s suggestion…

Cheers,   Jody

```python

import matplotlib
matplotlib.use('Qt5Agg')

import matplotlib.pyplot as plt
import numpy as np

class Picker(object):

	def __init__(self):
		self.x = np.array([])
		self.y = np.array([])

	def process_key(self, event):
		print("Key:", event.key)

	def process_button(self, event):
		print("Button:", event.x, event.y, event.xdata, event.ydata, 
event.button)
		self.x = np.append(self.x, event.xdata)
		self.y = np.append(self.y, event.ydata)

	def get_x(self):
		return self.x

	def get_y(self):
		return self.y

fig, ax = plt.subplots(1, 1)
picker = Picker()
fig.canvas.mpl_connect('key_press_event', picker.process_key)
fig.canvas.mpl_connect('button_press_event', picker.process_button)
plt.show()

print(picker.x)  #
print(picker.get_x())  # the same
print(picker.get_x().mean()) # returns the mean of x.
print(picker.get_y())
print(picker.get_y().mean())

```


On 2 Sep 2017, at 18:08, Benjamin Root wrote:

> If you assign a class method as the callbacks, such as 
> process_button(self,
> event), then that method could save the relevant values to itself. I 
> show
> how to do this in my book (as well as the global approach, too).
>
> Cheers!
> Ben Root
>
> On Sat, Sep 2, 2017 at 10:30 AM, Jody Klymak <jklymak at uvic.ca> wrote:
>
>> Hi Jean-Philippe
>>
>> There may be a fancier way, but you can just declare a global in
>> process_button to pass the value to a global variable.
>>
>> Cheers, Jody
>>
>> import matplotlib.pyplot as plt
>>
>> x = []
>>
>> def process_key(event):
>>     print("Key:", event.key)
>> def process_button(event):
>>     global x
>>     print("Button:", event.x, event.y, event.xdata, event.ydata, 
>> event.button)
>>     x += [event.xdata]
>>
>> fig, ax = plt.subplots(1, 1)
>> fig.canvas.mpl_connect('key_press_event', process_key)
>> fig.canvas.mpl_connect('button_press_event', process_button)
>> plt.show()
>>
>> print(x)
>>
>>
>> On 2 Sep 2017, at 7:01, Jean-Philippe Grivet wrote:
>>
>> Hi
>> Thank you for the very interesting refeerences. However, I find that 
>> the
>> various programs are rather
>> involved and that they do not exactly answer my needs. The simplest
>> program is probably the following
>> (from the boook by B. Root). It seems to be a step in the right 
>> direction!
>>
>> import matplotlib.pyplot as plt
>>
>> def process_key(event):
>> print("Key:", event.key)
>> def process_button(event):
>> print("Button:", event.x, event.y, event.xdata, event.ydata, 
>> event.button)
>>
>> fig, ax = plt.subplots(1, 1)
>> fig.canvas.mpl_connect('key_press_event', process_key)
>> fig.canvas.mpl_connect('button_press_event', process_button)
>> plt.show()
>>
>> So now, how do I retrieve the values event.xdata, event.ydata 
>> s(everal
>> times) in
>> order to use them in the main program ? (By the way, this is pretty 
>> easy
>> in Matlab: the function xclick the mouse coordinates and index of the
>> button
>> pressed).
>> Thank you soluch for your help.
>> JP Grivet
>>
>>
>> Le 30/08/2017 04:13, Thomas Caswell a écrit :
>>
>> Jean,
>>
>> What you want to do is totally possible!
>>
>> I suggest having a look at the examples in https://matplotlib.org/
>> examples/widgets/index.html the `ginput` method,
>> https://github.com/tacaswell/interactive_mpl_tutorial and Ben Root's 
>> book
>> https://www.amazon.com/Interactive-Applications-
>> using-Matplotlib-Benjamin/dp/1783988843
>>
>> Tom
>>
>> ---
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>> par le
>> logiciel antivirus Avast.
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>>
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