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plot_flip.py
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plot_flip.py
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r"""
Flip along an axis
==================
This example shows how to use the :py:class:`pylops.Flip`
operator to simply flip an input signal along an axis.
"""
import numpy as np
import matplotlib.pyplot as plt
import pylops
plt.close('all')
###############################################################################
# Let's start with a 1D example. Define an input signal composed of
# ``nt`` samples
nt = 10
x = np.arange(nt)
###############################################################################
# We can now create our flip operator and apply it to the input
# signal. We can also apply the adjoint to the flipped signal and we can
# see how for this operator the adjoint is effectively equivalent to
# the inverse.
Fop = pylops.Flip(nt)
y = Fop*x
xadj = Fop.H*y
plt.figure(figsize=(3, 5))
plt.plot(x, 'k', lw=3, label=r'$x$')
plt.plot(y, 'r', lw=3, label=r'$y=Fx$')
plt.plot(xadj, '--g', lw=3, label=r'$x_{adj} = F^H y$')
plt.title('Flip in 1st direction', fontsize=14, fontweight='bold')
plt.legend()
###############################################################################
# Let's now repeat the same exercise on a two dimensional signal. We will
# first flip the model along the first axis and then along the second axis
nt, nx = 10, 5
x = np.outer(np.arange(nt), np.ones(nx))
Fop = pylops.Flip(nt*nx, dims=(nt, nx), dir=0)
y = Fop*x.flatten()
xadj = Fop.H*y.flatten()
y = y.reshape(nt, nx)
xadj = xadj.reshape(nt, nx)
fig, axs = plt.subplots(1, 3, figsize=(7, 3))
fig.suptitle('Flip in 1st direction for 2d data', fontsize=14,
fontweight='bold', y=0.95)
axs[0].imshow(x, cmap='rainbow')
axs[0].set_title(r'$x$')
axs[0].axis('tight')
axs[1].imshow(y, cmap='rainbow')
axs[1].set_title(r'$y = F x$')
axs[1].axis('tight')
axs[2].imshow(xadj, cmap='rainbow')
axs[2].set_title(r'$x_{adj} = F^H y$')
axs[2].axis('tight')
plt.tight_layout()
plt.subplots_adjust(top=0.8)
x = np.outer(np.ones(nt), np.arange(nx))
Fop = pylops.Flip(nt*nx, dims=(nt, nx), dir=1)
y = Fop*x.flatten()
xadj = Fop.H*y.flatten()
y = y.reshape(nt, nx)
xadj = xadj.reshape(nt, nx)
# sphinx_gallery_thumbnail_number = 3
fig, axs = plt.subplots(1, 3, figsize=(7, 3))
fig.suptitle('Flip in 2nd direction for 2d data', fontsize=14,
fontweight='bold', y=0.95)
axs[0].imshow(x, cmap='rainbow')
axs[0].set_title(r'$x$')
axs[0].axis('tight')
axs[1].imshow(y, cmap='rainbow')
axs[1].set_title(r'$y = F x$')
axs[1].axis('tight')
axs[2].imshow(xadj, cmap='rainbow')
axs[2].set_title(r'$x_{adj} = F^H y$')
axs[2].axis('tight')
plt.tight_layout()
plt.subplots_adjust(top=0.8)