Re: [Matplotlib-users] Matplotlib drag overlapping points interactively

[Joe K. <jof...@gm...>]

Hi Yi,

I also posted this as an answer to your question on SO, but here's how I'd
approach it.

It's simplest to just have a "DraggablePoints" class that accepts multiple
artists.  That way you can synchronize which artist is "active" and ignore
the others.

As an example, based on yours:

import matplotlib.pyplot as plt
import matplotlib.patches as patches

class DraggablePoints(object):
    def __init__(self, artists, tolerance=5):
        for artist in artists:
            artist.set_picker(tolerance)
        self.artists = artists
        self.currently_dragging = False
        self.current_artist = None
        self.offset = (0, 0)

        for canvas in set(artist.figure.canvas for artist in self.artists):
            canvas.mpl_connect('button_press_event', self.on_press)
            canvas.mpl_connect('button_release_event', self.on_release)
            canvas.mpl_connect('pick_event', self.on_pick)
            canvas.mpl_connect('motion_notify_event', self.on_motion)

    def on_press(self, event):
        self.currently_dragging = True

    def on_release(self, event):
        self.currently_dragging = False
        self.current_artist = None

    def on_pick(self, event):
        if self.current_artist is None:
            self.current_artist = event.artist
            x0, y0 = event.artist.center
            x1, y1 = event.mouseevent.xdata, event.mouseevent.ydata
            self.offset = (x0 - x1), (y0 - y1)

    def on_motion(self, event):
        if not self.currently_dragging:
            return
        if self.current_artist is None:
            return
        dx, dy = self.offset
        self.current_artist.center = event.xdata + dx, event.ydata + dy
        self.current_artist.figure.canvas.draw()

if __name__ == '__main__':
    fig, ax = plt.subplots()
    ax.set(xlim=[-1, 2], ylim=[-1, 2])

    circles = [patches.Circle((0.32, 0.3), 0.2, fc='r', alpha=0.5),
               patches.Circle((0.3, 0.3), 0.2, fc='b', alpha=0.5)]
    for circ in circles:
        ax.add_patch(circ)

    dr = DraggablePoints(circles)
    plt.show()

Hope that helps!
-Joe


On Sat, Feb 8, 2014 at 7:32 PM, Yi <ide...@gm...> wrote:

> Hi Matplotlib community:
>
> In my case, I only want to drag one point each time. However, since the
> two points are heavily overlapping, dragging one point would cause another
> point to be dragged. How can I only drag one of the point? Thank you!
>
>
> from pylab import *from scipy import *import matplotlib.pyplot as pltimport matplotlib.patches as patches
>
> class DraggablePoint:
>     def __init__(self, p):
>         self.point = p
>         self.press = None
>
>     def connect(self):
>         self.cidpress = self.point.figure.canvas.mpl_connect('button_press_event', self.button_press_event)
>         self.cidrelease = self.point.figure.canvas.mpl_connect('button_release_event', self.button_release_event)
>         self.cidmotion = self.point.figure.canvas.mpl_connect('motion_notify_event', self.motion_notify_event)
>
>     def disconnect(self):
>     'disconnect all the stored connection ids'
>         self.point.figure.canvas.mpl_disconnect(self.cidpress)
>         self.point.figure.canvas.mpl_disconnect(self.cidrelease)
>         self.point.figure.canvas.mpl_disconnect(self.cidmotion)
>
>
>     def button_press_event(self,event):
>         if event.inaxes != self.point.axes:
>             return
>         contains = self.point.contains(event)[0]
>         if not contains: return
>         self.press = self.point.center, event.xdata, event.ydata
>
>
>     def button_release_event(self,event):
>         self.press = None
>         self.point.figure.canvas.draw()
>
>     def motion_notify_event(self, event):
>         if self.press is None: return
>         if event.inaxes != self.point.axes: return
>         self.point.center, xpress, ypress = self.press
>         dx = event.xdata - xpress
>         dy = event.ydata - ypress
>         self.point.center = (self.point.center[0]+dx, self.point.center[1]+dy)
>         print self.point.center
>         self.point.figure.canvas.draw()
> if __name__ == '__main__':
>     fig = plt.figure()
>     ax = fig.add_subplot(111)
>     ax.set_xlim(-1,2)
>     ax.set_ylim(-1,2)
>     circles = []
>     circle1 = patches.Circle((0.32,0.3), 0.2, fc='r', alpha=0.5, picker=True)
>     circle = patches.Circle((0.3,0.3), 0.2, fc='b', alpha=0.5, picker=True)
>     circles.append(ax.add_patch(circle1))
>     circles.append(ax.add_patch(circle))
>     drs = []
>     for c in circles:
>         #print c.center[0]
>         dr = DraggablePoint(c)
>         dr.connect()
>         drs.append(dr)
>     plt.show()
>
>
>
>
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