viscid.mapfield module

utility for translating spherical fields (theta, phi) <-> (lat, lon)

viscid.mapfield.as_mapfield(fld, order=('lon', 'lat'), units='')

Make sure a field has (lon, lat) coordinates

Parameters:

• fld (Field) – some field to transform
• order (tuple, optional) – Desired axes of the result
• units (str, optional) – units of the result (deg/rad)

Returns:

a field with (lon, lat) coordinates. The data will be loaded into memory if not already.

Return type:

Viscid.Field

viscid.mapfield.as_spherefield(fld, order=('phi', 'theta'), units='')

Make sure fld has (phi, theta) coordinates

fld (Field): some field to transform order (tuple, optional): Desired axes of the result units (str, optional): units of the result (deg/rad)

Returns:a field with (lon, lat) coordinates. The data will be loaded into memory if not already. Return type:Viscid.Field

viscid.mapfield.as_polar_mapfield(fld, bounding_lat=None, hemisphere='north', make_periodic=False)

Prepare a theta/phi or lat/lon field for polar projection

Parameters:

• fld (Field) – Some scalar or vector field
• bounding_lat (float, optional) – Used to slice the field, i.e., gives data from the pole to bounding_lat degrees equator-ward of the pole
• hemisphere (str, optional) – ‘north’ or ‘south’

Returns:

a field that can be mapfield plotted on polar axes

Return type:

Field

Raises:

ValueError – on bad hemisphere

viscid.mapfield.pts2polar_mapfield(pts, pts_axes, pts_unit='deg', hemisphere='north')

Prepare theta/phi or lat/lon points for a polar plot

Parameters:

• pts (ndarray) – A 2xN array of N points where the spatial dimensions encode phi, theta, lat, or lon.
• pts_axes (sequence) – sequence of strings that say what each axis of pts encodes, i.e., (‘theta’, ‘phi’).
• pts_unit (str, optional) – units of pts (‘deg’ or ‘rad’)
• hemisphere (str, optional) – ‘north’ or ‘south’

Returns:

2xN array of N points in radians where the axes are (‘lon’, ‘lat’), such that they can be given straight to matplotlib.pyplot.plot()

Return type:

ndarray

Raises:

ValueError – On bad pts_axes

Example

This example plots total field align currents in the northern hemisphere, then plots a curve onto the same plot

>>> f = viscid.load_file("$SRC/Viscid/sample/*_xdmf.iof.*.xdmf")
>>> vlt.plot(1e9 * f['fac_tot'], symmetric=True)
>>> # now make a curve from dawn to dusk spanning 20deg in lat
>>> N = 64
>>> pts = np.vstack([np.linspace(-90, 90, N),
                     np.linspace(10, 30, N)])
>>> pts_polar = viscid.pts2polar_mapfield(pts, ('phi', 'theta'),
                                          pts_unit='deg')
>>> plt.plot(pts_polar[0], pts_polar[1])
>>> vlt.show()

viscid.mapfield.convert_coordinates(fld, order, crd_mapping, units='')

Convert a Field’s coordinates

Parameters:

• fld (Field) – Description
• order (sequence) – target coordinates
• crd_mapping (dict) – summarizes functions that go from base -> target
• units (str, optional) – Additional info if you need to convert units too

Raises:

RuntimeError – If no mapping is found to go base -> target

viscid.mapfield.lat2theta(lat, unit='deg')

spherical latitude -> theta transformation

viscid.mapfield.lon2phi(lon, unit='deg')

spherical longitude -> phi transform; currently a no-op

viscid.mapfield.phi2lon(phi, unit='deg')

spherical phi -> longitude transform; currently a no-op

viscid.mapfield.theta2lat(theta, unit='deg')

spherical theta -> latitude transformation

viscid.mapfield.cart2sph(arr, deg=False)

Convert cartesian points to spherical (rad by default)

Parameters:

• arr (sequence) – shaped (3, ) or (3, N) for N xyz points
• deg (bool) – if result should be in degrees

Returns:

shaped (3, ) or (3, N) r, theta, phi points in radians

by default

Return type:

ndarray

viscid.mapfield.cart2latlon(arr, deg=True)

Convert latitude longitude (deg by default) to cartesian

Parameters:

• arr (sequence) – shaped (3, ) or (3, N) for N r, theta, phi points in radians by default
• deg (bool) – if arr is in dergrees

Returns:

shaped (2, ) or (2, N) xyz

Return type:

ndarray

viscid.mapfield.sph2cart(arr, deg=False)

Convert cartesian points to spherical (rad by default)

Parameters:

• arr (sequence) – shaped (3, ) or (3, N) for N r, theta, phi points in radians by default
• deg (bool) – if arr is in dergrees

Returns:

shaped (3, ) or (3, N) xyz

Return type:

ndarray

viscid.mapfield.latlon2cart(arr, r=1.0, deg=True)

Convert cartesian points to latitude longitude (deg by default)

Parameters:

• arr (sequence) – shaped (2, ) or (2, N) for N r, theta, phi points in radians by default
• deg (bool) – if arr is in dergrees

Returns:

shaped (3, ) or (3, N) xyz

Return type:

ndarray

viscid.mapfield.great_circle(p1, p2, origin=(0, 0, 0), n=32)

Get great circle path between two points in 3d

Parameters:

• p1 (sequence) – first point as [x, y, z]
• p2 (sequence) – second point as [x, y, z]
• origin (sequence) – origin of the sphere
• n (int) – Number of line segments along the great circle

Returns:

3xN ndarray