Matplotlib: draw a selection in a rectangle shape with the mouse

Question

I want to be able to draw a selection area on a matplotlib chart with a mouse event. I did not find information on how to do this with python.

In the end, I want to draw the region of interest with the mouse on the map created using the matplotlib base map, and get the angular coordinates.

Anyone have an idea like links?

Thanks,

Greg

class Annotate(object): def __init__(self): self.ax = plt.gca() self.rect = Rectangle((0,0), 1, 1, facecolor='None', edgecolor='green') self.x0 = None self.y0 = None self.x1 = None self.y1 = None self.ax.add_patch(self.rect) self.ax.figure.canvas.mpl_connect('button_press_event', self.on_press) self.ax.figure.canvas.mpl_connect('button_release_event', self.on_release) self.ax.figure.canvas.mpl_connect('motion_notify_event', self.on_motion) def on_press(self, event): print 'press' self.x0 = event.xdata self.y0 = event.ydata self.x1 = event.xdata self.y1 = event.ydata self.rect.set_width(self.x1 - self.x0) self.rect.set_height(self.y1 - self.y0) self.rect.set_xy((self.x0, self.y0)) self.rect.set_linestyle('dashed') self.ax.figure.canvas.draw() def on_motion(self,event): if self.on_press is True: return self.x1 = event.xdata self.y1 = event.ydata self.rect.set_width(self.x1 - self.x0) self.rect.set_height(self.y1 - self.y0) self.rect.set_xy((self.x0, self.y0)) self.rect.set_linestyle('dashed') self.ax.figure.canvas.draw() def on_release(self, event): print 'release' self.x1 = event.xdata self.y1 = event.ydata self.rect.set_width(self.x1 - self.x0) self.rect.set_height(self.y1 - self.y0) self.rect.set_xy((self.x0, self.y0)) self.rect.set_linestyle('solid') self.ax.figure.canvas.draw() print self.x0,self.x1,self.y0,self.y1 return [self.x0,self.x1,self.y0,self.y1] 

Answer 1

Matplotlib provides its own RectangleSelector . an example on the matplotlib page that you can adapt to your needs.

A simplified version will look something like this:

 import matplotlib.pyplot as plt import numpy as np from matplotlib.widgets import RectangleSelector xdata = np.linspace(0,9*np.pi, num=301) ydata = np.sin(xdata) fig, ax = plt.subplots() line, = ax.plot(xdata, ydata) def line_select_callback(eclick, erelease): x1, y1 = eclick.xdata, eclick.ydata x2, y2 = erelease.xdata, erelease.ydata rect = plt.Rectangle( (min(x1,x2),min(y1,y2)), np.abs(x1-x2), np.abs(y1-y2) ) ax.add_patch(rect) rs = RectangleSelector(ax, line_select_callback, drawtype='box', useblit=False, button=[1], minspanx=5, minspany=5, spancoords='pixels', interactive=True) plt.show() 

Answer 2

Here is a small example showing how to use the mouse to draw a rectangle on a matplotlib chart.

 import matplotlib.pyplot as plt from matplotlib.patches import Rectangle class Annotate(object): def __init__(self): self.ax = plt.gca() self.rect = Rectangle((0,0), 1, 1) self.x0 = None self.y0 = None self.x1 = None self.y1 = None self.ax.add_patch(self.rect) self.ax.figure.canvas.mpl_connect('button_press_event', self.on_press) self.ax.figure.canvas.mpl_connect('button_release_event', self.on_release) def on_press(self, event): print 'press' self.x0 = event.xdata self.y0 = event.ydata def on_release(self, event): print 'release' self.x1 = event.xdata self.y1 = event.ydata self.rect.set_width(self.x1 - self.x0) self.rect.set_height(self.y1 - self.y0) self.rect.set_xy((self.x0, self.y0)) self.ax.figure.canvas.draw() a = Annotate() plt.show()