r"""
Transpose
=========
This example shows how to use the :py:class:`pylops.Transpose`
operator. For arrays that are 2-dimensional in nature this operator
simply transposes rows and columns. For multi-dimensional arrays, this
operator can be used to permute dimensions
"""
import numpy as np
import matplotlib.pyplot as plt
import pylops

plt.close('all')
np.random.seed(0)

###############################################################################
# Let's start by creating a 2-dimensional array
dims = (20, 40)
x = np.arange(800).reshape(dims)

###############################################################################
# We use now the :py:class:`pylops.Transpose` operator to swap the two
# dimensions. As you will see the adjoint of this operator brings the data
# back to its original model, or in other words the adjoint operator is equal
# in this case to the inverse operator.
Top = pylops.Transpose(dims=dims, axes=(1,0))

y = Top * x.ravel()
xadj = Top.H * y
y = y.reshape(Top.dimsd)
xadj = xadj.reshape(Top.dims)

fig, axs = plt.subplots(1, 3, figsize=(10, 2))
fig.suptitle('Transpose for 2d data', fontsize=14, fontweight='bold', y=1.15)
axs[0].imshow(x, cmap='rainbow', vmin=0, vmax=800)
axs[0].set_title(r'$x$')
axs[0].axis('tight')
axs[1].imshow(y, cmap='rainbow', vmin=0, vmax=800)
axs[1].set_title(r'$y = F x$')
axs[1].axis('tight')
axs[2].imshow(xadj, cmap='rainbow', vmin=0, vmax=800)
axs[2].set_title(r'$x_{adj} = F^H y$')
axs[2].axis('tight')

###############################################################################
# A similar approach can of course be taken two swap multiple axes of
# multi-dimensional arrays for any number of dimensions.