r"""
Diagonal
========
This example shows how to use the :py:class:`pylops.Diagonal` operator
to perform *Element-wise multiplication* between the input vector and a vector :math:`\mathbf{d}`.

In other words, the operator acts as a  diagonal operator :math:`\mathbf{D}` whose elements along
the diagonal are the elements of the vector :math:`\mathbf{d}`.

"""
import matplotlib.gridspec as pltgs
import matplotlib.pyplot as plt
import numpy as np

import pylops

plt.close("all")

###############################################################################
# Let's define a diagonal operator :math:`\mathbf{d}` with increasing numbers from
# ``0`` to ``N`` and a unitary model :math:`\mathbf{x}`.
N = 10
d = np.arange(N)
x = np.ones(N)

Dop = pylops.Diagonal(d)

y = Dop * x
y1 = Dop.H * x

gs = pltgs.GridSpec(1, 6)
fig = plt.figure(figsize=(7, 4))
ax = plt.subplot(gs[0, 0:3])
im = ax.imshow(Dop.matrix(), cmap="rainbow", vmin=0, vmax=N)
ax.set_title("A", size=20, fontweight="bold")
ax.set_xticks(np.arange(N - 1) + 0.5)
ax.set_yticks(np.arange(N - 1) + 0.5)
ax.grid(linewidth=3, color="white")
ax.xaxis.set_ticklabels([])
ax.yaxis.set_ticklabels([])
ax.axis("tight")
ax = plt.subplot(gs[0, 3])
ax.imshow(x[:, np.newaxis], cmap="rainbow", vmin=0, vmax=N)
ax.set_title("x", size=20, fontweight="bold")
ax.set_xticks([])
ax.set_yticks(np.arange(N - 1) + 0.5)
ax.grid(linewidth=3, color="white")
ax.xaxis.set_ticklabels([])
ax.yaxis.set_ticklabels([])
ax = plt.subplot(gs[0, 4])
ax.text(
    0.35,
    0.5,
    "=",
    horizontalalignment="center",
    verticalalignment="center",
    size=40,
    fontweight="bold",
)
ax.axis("off")
ax = plt.subplot(gs[0, 5])
ax.imshow(y[:, np.newaxis], cmap="rainbow", vmin=0, vmax=N)
ax.set_title("y", size=20, fontweight="bold")
ax.set_xticks([])
ax.set_yticks(np.arange(N - 1) + 0.5)
ax.grid(linewidth=3, color="white")
ax.xaxis.set_ticklabels([])
ax.yaxis.set_ticklabels([])
fig.colorbar(im, ax=ax, ticks=[0, N], pad=0.3, shrink=0.7)
plt.tight_layout()

###############################################################################
# Similarly we can consider the input model as composed of two or more
# dimensions. In this case the diagonal operator can be still applied to
# each element or broadcasted along a specific direction. Let's start with the
# simplest case where each element is multipled by a different value
nx, ny = 3, 5
x = np.ones((nx, ny))
print(f"x =\n{x}")

d = np.arange(nx * ny).reshape(nx, ny)
Dop = pylops.Diagonal(d)

y = Dop * x.ravel()
y1 = Dop.H * x.ravel()

print(f"y = D*x =\n{y.reshape(nx, ny)}")
print(f"xadj = D'*x =\n{y1.reshape(nx, ny)}")

###############################################################################
# And we now broadcast
nx, ny = 3, 5
x = np.ones((nx, ny))
print(f"x =\n{x}")

# 1st dim
d = np.arange(nx)
Dop = pylops.Diagonal(d, dims=(nx, ny), axis=0)

y = Dop * x.ravel()
y1 = Dop.H * x.ravel()

print(f"1st dim: y = D*x =\n{y.reshape(nx, ny)}")
print(f"1st dim: xadj = D'*x =\n{y1.reshape(nx, ny)}")

# 2nd dim
d = np.arange(ny)
Dop = pylops.Diagonal(d, dims=(nx, ny), axis=1)

y = Dop * x.ravel()
y1 = Dop.H * x.ravel()

print(f"2nd dim: y = D*x =\n{y.reshape(nx, ny)}")
print(f"2nd dim: xadj = D'*x =\n{y1.reshape(nx, ny)}")