pyrfu.pyrf.pvi

pyrfu.pyrf.pvi(inp, scale: int = 10)

Returns the Partial Variance of Increments (PVI) of a time series.

\[PVI_i = \frac{|x_{i+s} - x_i|}{\sqrt{<|x_{i+s} - x_i|^2>}}\]

where \(s\) is the scale and the average \(<.>\) is taken over the whole interval, ignoring NaNs [1]. The increment \(x_{i+s} - x_i\) is given at the time of \(x_i\).

Parameters:

• inp (xarray.DataArray) – Input time series.

• scale (int, Optional) – Scale at which to compute the PVI, in number of samples. Default is 10.

Returns:

values – An xarray containing the pvi of the original time series.

Return type:

xarray.DataArray

Raises:

ValueError – If scale is not a positive integer.

References

[1]

Greco, A., P. Chuychai, W. H. Matthaeus, S. Servidio, and P. Dmitruk (2008), Intermittent MHD structures and classical discontinuities, Geophys. Res. Lett., 35, L19111, doi: https://doi.org/10.1029/2008GL035454.