CODEWITHSUNDEEP
pythonplotmatplotlibtkinterzooming
maupertius
maupertius

Reputation: 1638

Preserve zoom settings in interactive navigation of matplotlib figure

Is there a way to preserve the interactive navigation settings of a figure such that the next time the figure is updated the Zoom/Pan characteristics don't go back to the default values? To be more specific, if a zoom in a figure, and then I update the plot, is it possible to make the new figure appear with the same zoom settings of the previous one? I am using Tkinter.

Upvotes: 3

Views: 6904

Answers (1)

Joe Kington
Joe Kington

Reputation: 284652

You need to update the image instead of making a new image each time. As an example:

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

class DummyPlot(object):
    def __init__(self):
        self.imsize = (10, 10)
        self.data = np.random.random(self.imsize)

        self.fig, self.ax = plt.subplots()
        self.im = self.ax.imshow(self.data)

        buttonax = self.fig.add_axes([0.45, 0.9, 0.1, 0.075])
        self.button = Button(buttonax, 'Update')
        self.button.on_clicked(self.update)

    def update(self, event):
        self.data += np.random.random(self.imsize) - 0.5
        self.im.set_data(self.data)
        self.im.set_clim([self.data.min(), self.data.max()])
        self.fig.canvas.draw()

    def show(self):
        plt.show()

p = DummyPlot()
p.show()

If you want to plot the data for the first time when you hit "update", one work-around is to plot dummy data first and make it invisible.

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

class DummyPlot(object):
    def __init__(self):
        self.imsize = (10, 10)
        self.data = np.random.random(self.imsize)
        self.fig, self.ax = plt.subplots()

        dummy_data = np.zeros(self.imsize)
        self.im = self.ax.imshow(dummy_data)
        self.im.set_visible(False)

        buttonax = self.fig.add_axes([0.45, 0.9, 0.1, 0.075])
        self.button = Button(buttonax, 'Update')
        self.button.on_clicked(self.update)

    def update(self, event):
        self.im.set_visible(True)
        self.data += np.random.random(self.imsize) - 0.5
        self.im.set_data(self.data)
        self.im.set_clim([self.data.min(), self.data.max()])
        self.fig.canvas.draw()

    def show(self):
        plt.show()

p = DummyPlot()
p.show()

Alternately, you could just turn auto-scaling off, and create a new image each time. This will be significantly slower, though.

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

class DummyPlot(object):
    def __init__(self):
        self.imsize = (10, 10)
        self.fig, self.ax = plt.subplots()

        self.ax.axis([-0.5, self.imsize[1] - 0.5, 
                      self.imsize[0] - 0.5, -0.5])
        self.ax.set_aspect(1.0)
        self.ax.autoscale(False)

        buttonax = self.fig.add_axes([0.45, 0.9, 0.1, 0.075])
        self.button = Button(buttonax, 'Update')
        self.button.on_clicked(self.update)

    def update(self, event):
        self.ax.imshow(np.random.random(self.imsize))
        self.fig.canvas.draw()

    def show(self):
        plt.show()

p = DummyPlot()
p.show()

Upvotes: 4

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