Accessing a matplotlib plot within a def

Question

I am trying to modify a plot within a mouseevent definition in matplotlib. My final endpoint is to be able to get the user to drag a greyed out area marking the starting and ending x coordinates, from which I can determine the local maxima/minima. This is where I am currently. While the first avxspan shows up in the plot, the second one doesnt. I know the mouseevent is triggered since the x,y coords are printed on console. Can someone tell me why this wouldnt work? Much appreciated.

fig=plt.figure()
plt.figure(fig.number)
plt.plot(data)
ax=plt.gca()
plt.figtext(0.25,0.92, "Calculate")
plt.figtext(0.66,0.92, "Clear")
ax.axvspan(1, 100, facecolor='0.5', alpha=0.5)

def start(event):
    global ax
    ax.axvspan(100, 200, facecolor='0.5', alpha=0.5)
    print 'button=%d, x=%d, y=%d, xdata=%f, ydata=%f'%(
        event.button, event.x, event.y, event.xdata, event.ydata)

cid = fig.canvas.mpl_connect('button_press_event', start)
plt.show()
fig.canvas.mpl_disconnect(cid)

M4rtini · Accepted Answer · 2014-02-10 19:18:06Z

1

You might wanna take a look at the matplotlib.widgets module.

A simple one liner, enables you to drag a area, and define a callback function to get the coordinates that span the area.

simple example

import matplotlib.pyplot as plt
import numpy as np
from matplotlib.widgets import SpanSelector

x = np.arange(10)
y = x**2

plt.plot(x,y)
ax=plt.gca()


def onselect(vmin, vmax):
    print vmin, vmax
span = SpanSelector(ax, onselect, 'horizontal')
plt.show()

answered Feb 10, 2014 at 19:18

M4rtini

13.6k4 gold badges37 silver badges42 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

coder21 Over a year ago

oh shit. Have been reinventing the wheel! Thanks for pointing out to that module. I am using this hereon.

unutbu · Accepted Answer · 2014-02-10 19:07:27Z

0

Call fig.canvas.draw() to update the figure:

def start(event):
    ax.axvspan(100, 200, facecolor='0.5', alpha=0.5)
    print 'button=%d, x=%d, y=%d, xdata=%f, ydata=%f'%(
        event.button, event.x, event.y, event.xdata, event.ydata)
    fig.canvas.draw()

answered Feb 10, 2014 at 19:07

unutbu

886k197 gold badges1.9k silver badges1.7k bronze badges

3 Comments

coder21 Over a year ago

Bow to the lord! Thanks so much for the quick and right answer:)

coder21 Over a year ago

For those who are interested, take a look below for a one-liner code for the final endpoint that I had referred to

coder21 Over a year ago

Well, you gave the solution to what i asked. Yes, he has given me a better approach to what i intend to do. Infact, I am using that right now. I dont want to mislead someone who is actually trying to figure out the redraw concept which I seemed to have not noticed, until now.

Collectives™ on Stack Overflow

Accessing a matplotlib plot within a def

2 Answers 2

1 Comment

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related