CODEWITHSUNDEEP
pythonmatplotlibjupyter-notebook
Matthew May
Matthew May

Reputation: 113

How to change the location of PolyCollection?

How can I change the location of a "matplotlib.collections.PolyCollection"?

I have created a PolyCollection, then I want to changed the location.

%matplotlib notebook
import matplotlib.pyplot as plt

p=plt.figure()

area=plt.gca().fill_between((0,4), 1, 2, facecolor='red', alpha=0.25)
type(area)

enter image description here

The document is here: https://matplotlib.org/api/collections_api.html#matplotlib.collections.PolyCollection

I think set_offsets() is the funtion to change the position. But I can not find example.

I have tried

area.set_offsets([[1.1, 2.1]])

have no effect.

Upvotes: 1

Views: 676

Answers (1)

ImportanceOfBeingErnest
ImportanceOfBeingErnest

Reputation: 339300

The PolyCollection created by fill_between does not use any offset. It is simply a Collection of Paths in data coordinates. Three possible ways to update the "position" of the PolyCollection that is created via fill_between:

Setting offset_position

In case you want to set an offset in data coordinates you need to tell it to apply this offset in data coordinates via area.set_offset_position("data")

import numpy as np
import matplotlib.pyplot as plt

p=plt.figure()

area=plt.gca().fill_between((0,4), 1, 2, facecolor='red', alpha=0.25)

area.set_offsets(np.array([[1.1, 2.1]]))

area.set_offset_position("data")

plt.show()

Change the path

You may change the Path if you like:

import numpy as np
import matplotlib.pyplot as plt

p=plt.figure()

area=plt.gca().fill_between((0,4), 1, 2, facecolor='red', alpha=0.25)

offset = np.array([1.1, 2.1])

area.get_paths()[0].vertices += offset

plt.gca().dataLim.update_from_data_xy(area.get_paths()[0].vertices)

plt.gca().autoscale()
plt.show()

Change the transform

import numpy as np
import matplotlib.transforms
import matplotlib.pyplot as plt

p=plt.figure()

area=plt.gca().fill_between((0,4), 1, 2, facecolor='red', alpha=0.25)

offset = np.array([1.1, 2.1])

transoffset = matplotlib.transforms.Affine2D().translate(*offset)
area.set_transform(transoffset + area.get_transform())

plt.show()

Upvotes: 2

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