Note
Go to the end to download the full example code
Viewlims#
Creates two identical panels. Zooming in on the right panel will show a rectangle in the first panel, denoting the zoomed region.
Note
This example exercises the interactive capabilities of Matplotlib, and this will not appear in the static documentation. Please run this code on your machine to see the interactivity.
You can copy and paste individual parts, or download the entire example using the link at the bottom of the page.
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.patches import Rectangle
# We just subclass Rectangle so that it can be called with an Axes
# instance, causing the rectangle to update its shape to match the
# bounds of the Axes
class UpdatingRect(Rectangle):
def __call__(self, ax):
self.set_bounds(*ax.viewLim.bounds)
ax.figure.canvas.draw_idle()
# A class that will regenerate a fractal set as we zoom in, so that you
# can actually see the increasing detail. A box in the left panel will show
# the area to which we are zoomed.
class MandelbrotDisplay:
def __init__(self, h=500, w=500, niter=50, radius=2., power=2):
self.height = h
self.width = w
self.niter = niter
self.radius = radius
self.power = power
def compute_image(self, xstart, xend, ystart, yend):
self.x = np.linspace(xstart, xend, self.width)
self.y = np.linspace(ystart, yend, self.height).reshape(-1, 1)
c = self.x + 1.0j * self.y
threshold_time = np.zeros((self.height, self.width))
z = np.zeros(threshold_time.shape, dtype=complex)
mask = np.ones(threshold_time.shape, dtype=bool)
for i in range(self.niter):
z[mask] = z[mask]**self.power + c[mask]
mask = (np.abs(z) < self.radius)
threshold_time += mask
return threshold_time
def ax_update(self, ax):
ax.set_autoscale_on(False) # Otherwise, infinite loop
# Get the number of points from the number of pixels in the window
self.width, self.height = \
np.round(ax.patch.get_window_extent().size).astype(int)
# Get the range for the new area
vl = ax.viewLim
extent = vl.x0, vl.x1, vl.y0, vl.y1
# Update the image object with our new data and extent
im = ax.images[-1]
im.set_data(self.compute_image(*extent))
im.set_extent(extent)
ax.figure.canvas.draw_idle()
md = MandelbrotDisplay()
Z = md.compute_image(-2., 0.5, -1.25, 1.25)
fig1, (ax1, ax2) = plt.subplots(1, 2)
ax1.imshow(Z, origin='lower',
extent=(md.x.min(), md.x.max(), md.y.min(), md.y.max()))
ax2.imshow(Z, origin='lower',
extent=(md.x.min(), md.x.max(), md.y.min(), md.y.max()))
rect = UpdatingRect(
[0, 0], 0, 0, facecolor='none', edgecolor='black', linewidth=1.0)
rect.set_bounds(*ax2.viewLim.bounds)
ax1.add_patch(rect)
# Connect for changing the view limits
ax2.callbacks.connect('xlim_changed', rect)
ax2.callbacks.connect('ylim_changed', rect)
ax2.callbacks.connect('xlim_changed', md.ax_update)
ax2.callbacks.connect('ylim_changed', md.ax_update)
ax2.set_title("Zoom here")
plt.show()