4.2.4. pde.grids.cartesian module¶
Cartesian grids of arbitrary dimension.
- class CartesianGrid(bounds, shape, periodic=False)[source]¶
Bases:
GridBase
d-dimensional Cartesian grid with uniform discretization for each axis
The grids can be thought of as a collection of n-dimensional boxes, called cells, of equal length in each dimension. The bounds then defined the total volume covered by these cells, while the cell coordinates give the location of the box centers. We index the boxes starting from 0 along each dimension. Consequently, the cell \(i-\frac12\) corresponds to the left edge of the covered interval and the index \(i+\frac12\) corresponds to the right edge, when the dimension is covered by d boxes.
In particular, the discretization along dimension \(k\) is defined as
\[\begin{split}x^{(k)}_i &= x^{(k)}_\mathrm{min} + \left(i + \frac12\right) \Delta x^{(k)} \quad \text{for} \quad i = 0, \ldots, N^{(k)} - 1 \\ \Delta x^{(k)} &= \frac{x^{(k)}_\mathrm{max} - x^{(k)}_\mathrm{min}}{N^{(k)}}\end{split}\]where \(N^{(k)}\) is the number of cells along this dimension. Consequently, cells have dimension \(\Delta x^{(k)}\) and cover the interval \([x^{(k)}_\mathrm{min}, x^{(k)}_\mathrm{max}]\).
- Parameters
bounds (list of tuple) – Give the coordinate range for each axis. This should be a tuple of two number (lower and upper bound) for each axis. The length of bounds thus determines the grid dimension.
shape (list) – The number of support points for each axis. The length of shape needs to match the grid dimension.
periodic (bool or list) – Specifies which axes possess periodic boundary conditions. This is either a list of booleans defining periodicity for each individual axis or a single boolean value specifying the same periodicity for all axes.
- boundary_names: Dict[str, Tuple[int, bool]] = {'back': (2, False), 'bottom': (1, False), 'front': (2, True), 'left': (0, False), 'right': (0, True), 'top': (1, True)}¶
Names of boundaries to select them conveniently
- Type
- property cell_volume_data¶
size associated with each cell
- classmethod from_bounds(bounds, shape, periodic)[source]¶
- Parameters
bounds (tuple) – Give the coordinate range for each axis. This should be a tuple of two number (lower and upper bound) for each axis. The length of bounds thus determines the grid dimension.
shape (tuple) – The number of support points for each axis. The length of shape needs to match the grid dimension.
periodic (bool or list) – Specifies which axes possess periodic boundary conditions. This is either a list of booleans defining periodicity for each individual axis or a single boolean value specifying the same periodicity for all axes.
- Returns
CartesianGrid
representing the region chosen by bounds- Return type
- from_polar_coordinates(distance, angle, origin=None)[source]¶
convert polar coordinates to Cartesian coordinates
This function is currently only implemented for 1d and 2d systems.
- Parameters
- Returns
The Cartesian coordinates corresponding to the given polar coordinates.
- Return type
- classmethod from_state(state)[source]¶
create a field from a stored state.
- Parameters
state (dict) – The state from which the grid is reconstructed.
- Return type
- get_line_data(data, extract='auto')[source]¶
return a line cut through the given data
- Parameters
data (
ndarray
) – The values at the grid pointsextract (str) –
Determines which cut is done through the grid. Possible choices are (default is cut_0):
cut_#: return values along the axis specified by # and use the mid point along all other axes.
project_#: average values for all axes, except axis #.
Here, # can either be a zero-based index (from 0 to dim-1) or a letter denoting the axis.
- Returns
A dictionary with information about the line cut, which is convenient for plotting.
- Return type
- get_random_point(*, boundary_distance=0, coords='cartesian', rng=None)[source]¶
return a random point within the grid
- Parameters
boundary_distance (float) – The minimal distance this point needs to have from all boundaries.
coords (str) – Determines the coordinate system in which the point is specified. Valid values are cartesian, cell, and grid; see
transform()
.rng (
Generator
) – Random number generator (default:default_rng()
)
- Returns
The coordinates of the point
- Return type
- iter_mirror_points(point, with_self=False, only_periodic=True)[source]¶
generates all mirror points corresponding to point
- plot(*args, title=None, filename=None, action='auto', ax_style=None, fig_style=None, ax=None, **kwargs)[source]¶
visualize the grid
- Parameters
title (str) – Title of the plot. If omitted, the title might be chosen automatically.
filename (str, optional) – If given, the plot is written to the specified file.
action (str) – Decides what to do with the final figure. If the argument is set to show,
matplotlib.pyplot.show()
will be called to show the plot. If the value is none, the figure will be created, but not necessarily shown. The value close closes the figure, after saving it to a file when filename is given. The default value auto implies that the plot is shown if it is not a nested plot call.ax_style (dict) – Dictionary with properties that will be changed on the axis after the plot has been drawn by calling
matplotlib.pyplot.setp()
. A special item i this dictionary is use_offset, which is flag that can be used to control whether offset are shown along the axes of the plot.fig_style (dict) – Dictionary with properties that will be changed on the figure after the plot has been drawn by calling
matplotlib.pyplot.setp()
. For instance, using fig_style={‘dpi’: 200} increases the resolution of the figure.ax (
matplotlib.axes.Axes
) – Figure axes to be used for plotting. The special value “create” creates a new figure, while “reuse” attempts to reuse an existing figure, which is the default.**kwargs – Extra arguments are passed on the to the matplotlib plotting routines, e.g., to set the color of the lines
- point_to_cartesian(points, *, full=False)[source]¶
convert coordinates of a point to Cartesian coordinates
- polar_coordinates_real(origin, *, ret_angle=False)[source]¶
return polar coordinates associated with the grid
- Parameters
origin (
ndarray
) – Coordinates of the origin at which the polar coordinate system is anchored.ret_angle (bool) – Determines whether angles are returned alongside the distance. If False only the distance to the origin is returned for each support point of the grid. If True, the distance and angles are returned. For a 1d system system, the angle is defined as the sign of the difference between the point and the origin, so that angles can either be 1 or -1. For 2d systems and 3d systems, polar coordinates and spherical coordinates are used, respectively.
- Return type
- class UnitGrid(shape, periodic=False)[source]¶
Bases:
CartesianGrid
d-dimensional Cartesian grid with unit discretization in all directions
The grids can be thought of as a collection of d-dimensional cells of unit length. The shape parameter determines how many boxes there are in each direction. The cells are enumerated starting with 0, so the last cell has index \(n-1\) if there are \(n\) cells along a dimension. A given cell \(i\) extends from coordinates \(i\) to \(i + 1\), so the midpoint is at \(i + \frac12\), which is the cell coordinate. Taken together, the cells covers the interval \([0, n]\) along this dimension.
- Parameters
shape (list) – The number of support points for each axis. The dimension of the grid is given by len(shape).
periodic (bool or list) – Specifies which axes possess periodic boundary conditions. This is either a list of booleans defining periodicity for each individual axis or a single boolean value specifying the same periodicity for all axes.
- to_cartesian()[source]¶
convert unit grid to
CartesianGrid
- Return type