graspfile.grid

This is the module for manipulating grid files containing one or more field cuts from TICRA Tools, GRASP and CHAMP

Classes

GraspField() Object holding a single dataset from a Grasp field on grid output file (*.grd)
GraspGrid() Object holding the data in contained in a general Grasp grid field output
class graspfile.grid.GraspField[source]

Bases: object

Object holding a single dataset from a Grasp field on grid output file (*.grd)

The field is held in a complex numpy array of shape (grid_n_x, grid_n_y, field_components) where grid_n_x and grid_n_y set the number of points in the grid and field_components is the number of field components

beam_center = None

Beam center in [x,y] form

Type:list
field = None

the array of complex field components. the field object is numpy array of shape (grid_n_x, grid_n_y, field_components)

Type:numpy.ndarray
field_components = None

Number of field components in grid.

Equivalent to the GRASP Grid file’s ncomp. 2 for far fields, 3 for near fields.

get_value(xv, yv)[source]

Return the value of the field at the nearest point to xv, yv

Parameters:
  • xv – float containing the x coordinate of the point to get.
  • yv – float containing the y coordinate of the point to get.
Returns:

ndarray – containing self.field_components values of the field at xv, yv
grid_max_x = None

Maximum extent of grid in 1st dimension

Type:float
grid_max_y = None

Maximum extent of grid in 2nd dimension

Type:float
grid_min_x = None

Minimum extent of grid in 1st dimension

Type:float
grid_min_y = None

Minimum extent of grid in 2nd dimension

Type:float
grid_n_x = None

Number of points in grid in 1st dimension

Type:int
grid_n_y = None

Number of points in grid in 2nd dimension

Type:int
grid_step_x = None

step size of grid in 1st dimension

Type:float
grid_step_y = None

step size of grid in 2nd dimension

Type:float
index_radial_dist(i, j)[source]

Return radial distance from the beam center to an element of the field.

Useful for calculating the integrated power in a beam within a certain radius.

k_limit = None

defines whether grid is filled or sparse * 0: filled * 1: sparse

Type:int
positions

Return meshed grids of the x and y positions of each point in the field

positions_1d

Return numpy arrays of the x and y positions used in the field

radius_grid(center=None)[source]

Return an array holding the radii of each point from the beam centre.

Parameters:center – tuple holding coordinates of the center to calculate the radius from
Returns:numpy.ndarray – numpy array with same shape as the field grid holding the radii.
read(fi, field_components)[source]

Reads the Grasp dataset from the file object passed in. This assumes that it is being called from the graspGrid classes read(fi) method, so that the file object is already at the start of the record

rotate_polarization(angle=45.0)[source]

Rotate the basis of the polarization by <angle>. Will only work on linear polarization types

*TODO: Implement checks for polarization type*

Parameters:angle – angle in degrees to rotate the polarization basis by.
Returns:nothing.
scale_field(scale_factor)[source]

Multiply the complex field by a scale factor.

Parameters:scale_factor (float – ): Multiplier.
write(fo)[source]

Write GRASP grid file to open file object fo

class graspfile.grid.GraspGrid[source]

Bases: object

Object holding the data in contained in a general Grasp grid field output

Create empty variables or lists of attributes for holding data for each dataset

beam_centers = None

list of beam centers for individual fields in the file.

Type:list
combine_fields(coherent=False, scale=True)[source]

Sum fields within the grid object.

Assumes that all fields have the same positions, size, etc.

Parameters:
  • coherent (bool) – If True, add complex values of fields directly, rather than adding powers.
  • scale (bool) – Scale the output by the number of fields to be added, so that a mean field is calculated. Scales by number of fields for coherent summation and by sqrt(number of fields) for incoherent summation.
field_components = None

number of field components.

Equivalent to the GRASP Grid file’s ncomp. 2 for far fields, 3 for near fields.

Type:int
fields = None

List of individual fields in file,

Type:list of (GraspField)
freq_unit = None

The unit that the frequencies are given in.

Type:str
freqs = None

List of frequencies in units of freq_unit

Type:list
header = None

List of lines in the header section of the file

Type:list of str
igrid = None

grid type.

Type of field grid. * 1 : uv-grid: (X; Y ) = (u; v) where u and v are the two first coordinates of the unit vector to the field

point. Hence, r^ = u; v; p = √(1 − u² − v²) where u and v are related to the spherical angles by u = sin θ cos φ; v = sin θ sin φ.
  • 4 : Elevation over azimuth: (X; Y )=(Az,El), where Az and El define the direction to the field point by
    r^ = − sin Az cos El; sin El; cos Az cos El.
  • 5 : Elevation and azimuth: (X; Y )=(Az,El), where Az and El define the direction to the field point through
    the relations Az = -θ cos φ; El = θ sin φ to the spherical angles θ and φ.
  • 6 : Azimuth over elevation: (X; Y )= (Az, El), where Az and El define the direction to the field point by
    r^ = − sin Az; cos Az sin El; cos Az cos El.
  • 7 : θφ-grid: (X; Y ) = (φ; θ), where θ and φ are the spherical angles of the direction to the field point.
  • 9 : Azimuth over elevation, EDX definition: (X; Y )=(Az,El), where Az and El define the direction to the
    field point by r^ = sin Az cos El; sin El; cos Az cos El.
  • 10 : Elevation over azimuth, EDX definition: (X; Y )= (Az, El), where Az and El define the direction to the
    field point by r^ = sin Az; cos Az sin El; cos Az cos El.
Type:int
ktype = None

type of file format.

Always 1 for TICRA Tools files.

Type:int
nset = None

number of grids in file.

Type:int
parse_header(header)[source]

Parse the header of a grid file for useful information

Parameters:header – list of lines in the header text.
polarization = None

type of field components.

Equivalent to the GRASP Grid file’s icomp.

Values signify the following polarization definitions
  • 1: Linear E_theta and E_phi.
  • 2: Right hand and left hand circular (Erhc and Elhc).
  • 3: Linear Eco and Ecx (Ludwig’s third definition).
  • 4: Linear along major and minor axes of the polarisation ellipse, Emaj and Emin.
  • 5: XPD fields: E_theta/E_phi and E_phi/E_theta.
  • 6: XPD fields: Erhc/Elhc and Elhc/Erhc.
  • 7: XPD fields: Eco/Ecx and Ecx/Eco.
  • 8: XPD fields: Emaj/Emin and Emin/Emaj.
  • 9: Total power |E| and Erhc=Elhc.
Type:int
read(fi)[source]

Reads GRASP output grid files from file object and fills a number of variables and numpy arrays with the data

rotate_polarization(angle=45.0)[source]

Rotate the polarization basis for each field in the GraspGrid

scale_fields(scale_factor)[source]

Multiply the complex fields by a scale factor.

Parameters:scale_factor (float – ): Multiplier.
write(fo)[source]

Write GRASP grid file to open file object fo