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.