pysteps.cascade.decomposition.decomposition_fft
pysteps.cascade.decomposition.decomposition_fft¶
- pysteps.cascade.decomposition.decomposition_fft(field, bp_filter, **kwargs)¶
Decompose a two-dimensional input field into multiple spatial scales by using the Fast Fourier Transform (FFT) and a set of bandpass filters.
- Parameters
- field: array_like
Two-dimensional array containing the input field. All values are required to be finite.
- bp_filter: dict
A filter returned by a method implemented in
pysteps.cascade.bandpass_filters.
- Returns
- out: ndarray
A dictionary described in the module documentation. The number of cascade levels is determined from the filter (see
pysteps.cascade.bandpass_filters).
- Other Parameters
- fft_method: str or tuple
A string or a (function,kwargs) tuple defining the FFT method to use (see
pysteps.utils.interface.get_method()). Defaults to “numpy”. This option is not used if input_domain and output_domain are both set to “spectral”.- normalize: bool
If True, normalize the cascade levels to zero mean and unit variance. Requires that compute_stats is True. Implies that compute_stats is True. Defaults to False.
- mask: array_like
Optional mask to use for computing the statistics for the cascade levels. Pixels with mask==False are excluded from the computations. This option is not used if output domain is “spectral”.
- input_domain: {“spatial”, “spectral”}
The domain of the input field. If “spectral”, the input is assumed to be in the spectral domain. Defaults to “spatial”.
- output_domain: {“spatial”, “spectral”}
If “spatial”, the output cascade levels are transformed back to the spatial domain by using the inverse FFT. If “spectral”, the cascade is kept in the spectral domain. Defaults to “spatial”.
- compute_stats: bool
If True, the output dictionary contains the keys “means” and “stds” for the mean and standard deviation of each output cascade level. Defaults to False.
- compact_output: bool
Applicable if output_domain is “spectral”. If set to True, only the parts of the Fourier spectrum with non-negligible filter weights are stored. Defaults to False.