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- Tabprm

# Tabprm

class `astropy.wcs.``Tabprm`

  Bases: `object`

  A class to store the information related to tabular coordinates, i.e., coordinates that are defined via a lookup table.

  This class can not be constructed directly from Python, but instead is returned from `tab`.

  Attributes Summary

  `K` | `int array[M]` (read-only) The lengths of the axes of the coordinate
  `M` | `int` (read-only) Number of tabular coordinate axes.
  `coord` | `double array[K_M]...[K_2][K_1][M]` The tabular coordinate array.
  `crval` | `double array[M]` Index values for the reference pixel for each of
  `delta` | `double array[M]` (read-only) Interpolated indices into the coord
  `extrema` | `double array[K_M]...[K_2][2][M]` (read-only)
  `map` | `int array[M]` Association between axes.
  `nc` | `int` (read-only) Total number of coord vectors in the coord array.
  `p0` | `int array[M]` Interpolated indices into the coordinate array.
  `sense` | `int array[M]` +1 if monotonically increasing, -1 if decreasing.

  Methods Summary

  `print_contents`() | Print the contents of the `Tabprm` object to stdout.
  `set`() | Allocates memory for work arrays.

  Attributes Documentation

  `K`

    `int array[M]` (read-only) The lengths of the axes of the coordinate array.

    An array of length `M` whose elements record the lengths of the axes of the coordinate array and of each indexing vector.

  `M`

    `int` (read-only) Number of tabular coordinate axes.

  `coord`

    `double array[K_M]...[K_2][K_1][M]` The tabular coordinate array.

    Has the dimensions:

        (K_M, ... K_2, K_1, M)

    (see `K`) i.e. with the `M` dimension varying fastest so that the `M` elements of a coordinate vector are stored contiguously in memory.

  `crval`

    `double array[M]` Index values for the reference pixel for each of the tabular coord axes.

  `delta`

    `double array[M]` (read-only) Interpolated indices into the coord array.

    Array of interpolated indices into the coordinate array such that Upsilon_m, as defined in Paper III, is equal to (`p0` [m] + 1) + delta[m].

  `extrema`

    `double array[K_M]...[K_2][2][M]` (read-only)

    An array recording the minimum and maximum value of each element of the coordinate vector in each row of the coordinate array, with the dimensions:

        (K_M, ... K_2, 2, M)

    (see `K`). The minimum is recorded in the first element of the compressed K_1 dimension, then the maximum. This array is used by the inverse table lookup function to speed up table searches.

  `map`

    `int array[M]` Association between axes.

    A vector of length `M` that defines the association between axis m in the M-dimensional coordinate array (1 <= m <= M) and the indices of the intermediate world coordinate and world coordinate arrays.

    When the intermediate and world coordinate arrays contain the full complement of coordinate elements in image-order, as will usually be the case, then `map[m-1] == i-1` for axis i in the N-dimensional image (1 <= i <= N). In terms of the FITS keywords:

        map[PVi_3a - 1] == i - 1.

    However, a different association may result if the intermediate coordinates, for example, only contains a (relevant) subset of intermediate world coordinate elements. For example, if M == 1 for an image with N > 1, it is possible to fill the intermediate coordinates with the relevant coordinate element with `nelem` set to 1. In this case `map[0] = 0` regardless of the value of i.

  `nc`

    `int` (read-only) Total number of coord vectors in the coord array.

    Total number of coordinate vectors in the coordinate array being the product K_1 * K_2 * ... * K_M.

  `p0`

    `int array[M]` Interpolated indices into the coordinate array.

    Vector of length `M` of interpolated indices into the coordinate array such that Upsilon_m, as defined in Paper III, is equal to `(p0[m] + 1) + delta[m]`.

  `sense`

    `int array[M]` +1 if monotonically increasing, -1 if decreasing.

    A vector of length `M` whose elements indicate whether the corresponding indexing vector is monotonically increasing (+1), or decreasing (-1).

  Methods Documentation

  `print_contents`()

    Print the contents of the `Tabprm` object to stdout. Probably only useful for debugging purposes, and may be removed in the future.

    To get a string of the contents, use `repr`.

  `set`()

    Allocates memory for work arrays.

    Also sets up the class according to information supplied within it.

    Note that this routine need not be called directly; it will be invoked by functions that need it.

    Raises:

    MemoryError :

    > Memory allocation failed.

    InvalidTabularParameters :

    > Invalid tabular parameters.