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Module « scipy.io »

Fonction loadmat - module scipy.io

Signature de la fonction loadmat

def loadmat(file_name, mdict=None, appendmat=True, *, spmatrix=True, **kwargs) 

Description

help(scipy.io.loadmat)

Load MATLAB file.

Parameters
----------
file_name : str
   Name of the mat file (do not need .mat extension if
   appendmat==True). Can also pass open file-like object.
mdict : dict, optional
    Dictionary in which to insert matfile variables.
appendmat : bool, optional
   True to append the .mat extension to the end of the given
   filename, if not already present. Default is True.
spmatrix : bool, optional (default: True)
    If ``True``, return sparse ``coo_matrix``. Otherwise return ``coo_array``.
    Only relevant for sparse variables.
byte_order : str or None, optional
   None by default, implying byte order guessed from mat
   file. Otherwise can be one of ('native', '=', 'little', '<',
   'BIG', '>').
mat_dtype : bool, optional
   If True, return arrays in same dtype as would be loaded into
   MATLAB (instead of the dtype with which they are saved).
squeeze_me : bool, optional
   Whether to squeeze unit matrix dimensions or not.
chars_as_strings : bool, optional
   Whether to convert char arrays to string arrays.
matlab_compatible : bool, optional
   Returns matrices as would be loaded by MATLAB (implies
   squeeze_me=False, chars_as_strings=False, mat_dtype=True,
   struct_as_record=True).
struct_as_record : bool, optional
   Whether to load MATLAB structs as NumPy record arrays, or as
   old-style NumPy arrays with dtype=object. Setting this flag to
   False replicates the behavior of scipy version 0.7.x (returning
   NumPy object arrays). The default setting is True, because it
   allows easier round-trip load and save of MATLAB files.
verify_compressed_data_integrity : bool, optional
    Whether the length of compressed sequences in the MATLAB file
    should be checked, to ensure that they are not longer than we expect.
    It is advisable to enable this (the default) because overlong
    compressed sequences in MATLAB files generally indicate that the
    files have experienced some sort of corruption.
variable_names : None or sequence
    If None (the default) - read all variables in file. Otherwise,
    `variable_names` should be a sequence of strings, giving names of the
    MATLAB variables to read from the file. The reader will skip any
    variable with a name not in this sequence, possibly saving some read
    processing.
simplify_cells : False, optional
    If True, return a simplified dict structure (which is useful if the mat
    file contains cell arrays). Note that this only affects the structure
    of the result and not its contents (which is identical for both output
    structures). If True, this automatically sets `struct_as_record` to
    False and `squeeze_me` to True, which is required to simplify cells.
uint16_codec : str, optional
    The codec to use for decoding characters, which are stored as uint16
    values. The default uses the system encoding, but this can be manually
    set to other values such as 'ascii', 'latin1', and 'utf-8'. This
    parameter is relevant only for files stored as v6 and above, and not
    for files stored as v4.

Returns
-------
mat_dict : dict
   dictionary with variable names as keys, and loaded matrices as values.

Notes
-----
v4 (Level 1.0), v6 and v7 to 7.2 matfiles are supported.

You will need an HDF5 Python library to read MATLAB 7.3 format mat
files. Because SciPy does not supply one, we do not implement the
HDF5 / 7.3 interface here.

Examples
--------
>>> from os.path import dirname, join as pjoin
>>> import scipy.io as sio

Get the filename for an example .mat file from the tests/data directory.

>>> data_dir = pjoin(dirname(sio.__file__), 'matlab', 'tests', 'data')
>>> mat_fname = pjoin(data_dir, 'testdouble_7.4_GLNX86.mat')

Load the .mat file contents.

>>> mat_contents = sio.loadmat(mat_fname, spmatrix=False)

The result is a dictionary, one key/value pair for each variable:

>>> sorted(mat_contents.keys())
['__globals__', '__header__', '__version__', 'testdouble']
>>> mat_contents['testdouble']
array([[0.        , 0.78539816, 1.57079633, 2.35619449, 3.14159265,
        3.92699082, 4.71238898, 5.49778714, 6.28318531]])

By default SciPy reads MATLAB structs as structured NumPy arrays where the
dtype fields are of type `object` and the names correspond to the MATLAB
struct field names. This can be disabled by setting the optional argument
`struct_as_record=False`.

Get the filename for an example .mat file that contains a MATLAB struct
called `teststruct` and load the contents.

>>> matstruct_fname = pjoin(data_dir, 'teststruct_7.4_GLNX86.mat')
>>> matstruct_contents = sio.loadmat(matstruct_fname)
>>> teststruct = matstruct_contents['teststruct']
>>> teststruct.dtype
dtype([('stringfield', 'O'), ('doublefield', 'O'), ('complexfield', 'O')])

The size of the structured array is the size of the MATLAB struct, not the
number of elements in any particular field. The shape defaults to 2-D
unless the optional argument `squeeze_me=True`, in which case all length 1
dimensions are removed.

>>> teststruct.size
1
>>> teststruct.shape
(1, 1)

Get the 'stringfield' of the first element in the MATLAB struct.

>>> teststruct[0, 0]['stringfield']
array(['Rats live on no evil star.'],
  dtype='<U26')

Get the first element of the 'doublefield'.

>>> teststruct['doublefield'][0, 0]
array([[ 1.41421356,  2.71828183,  3.14159265]])

Load the MATLAB struct, squeezing out length 1 dimensions, and get the item
from the 'complexfield'.

>>> matstruct_squeezed = sio.loadmat(matstruct_fname, squeeze_me=True)
>>> matstruct_squeezed['teststruct'].shape
()
>>> matstruct_squeezed['teststruct']['complexfield'].shape
()
>>> matstruct_squeezed['teststruct']['complexfield'].item()
array([ 1.41421356+1.41421356j,  2.71828183+2.71828183j,
    3.14159265+3.14159265j])


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