Inspired by this example I'm trying to write a little matplotlib program that allows the user to drag and drop datapoints in a scatter plot dynamically. In contrast to the example which uses a bar plot (and thus allows dragging of rectangles) my goal was to achieve the same with other patches, like for instance a circle (any patch that is more scatter-plot-compatible than a rectangle would do). However I'm stuck at the point of updating the position of my patch. While a Rectangle
provides a function set_xy
I cannot find a direct analog for Cirlce
or Ellipse
. Obtaining the position of a circle is also less straightforward that for a rectangle, but is possible via obtaining the bounding box. The missing piece now is to find a way to update the position of my patch. Any hint on how to achieve this would be great! The current minimal working example would look like this:
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as patches
class DraggablePatch:
def __init__(self, patch):
self.patch = patch
self.storedPosition = None
self.connect()
def getPosOfPatch(self, marker):
ext = marker.get_extents().get_points()
x0 = ext[0,0]
y0 = ext[0,1]
x1 = ext[1,0]
y1 = ext[1,1]
return 0.5*(x0+x1), 0.5*(y0+y1)
def connect(self):
'connect to all the events we need'
self.cidpress = self.patch.figure.canvas.mpl_connect('button_press_event', self.onPress)
self.cidmotion = self.patch.figure.canvas.mpl_connect('motion_notify_event', self.onMove)
def onPress(self, event):
'on button press we will see if the mouse is over us and store some data'
contains, attrd = self.patch.contains(event)
if contains:
self.storedPosition = self.getPosOfPatch(self.patch), event.xdata, event.ydata
def onMove(self, event):
'how to update an circle?!'
contains, attrd = self.patch.contains(event)
if contains and self.storedPosition is not None:
oldPos, oldEventXData, oldEventYData = self.storedPosition
dx = event.xdata - oldEventXData
dy = event.ydata - oldEventYData
newX = oldPos[0] + dx
newY = oldPos[1] + dy
print "now I would like to move my patch to", newX, newY
def myPatch(x,y):
return patches.Circle((x,y), radius=.05, alpha=0.5)
N = 10
x = np.random.random(N)
y = np.random.random(N)
patches = [myPatch(x[i], y[i]) for i in range(N)]
fig = plt.figure()
ax = fig.add_subplot(111)
drs = []
for patch in patches:
ax.add_patch(patch)
dr = DraggablePatch(patch)
drs.append(dr)
plt.show()
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