myimagelib.corrLib.vacf_piv¶

myimagelib.corrLib.vacf_piv(vstack, dt, mode='direct')¶

Compute averaged vacf from PIV data. This is a wrapper of function autocorr_t(), adding the averaging over all the velocity spots.

Parameters

vstack – a 2-D np array of velocity data. axis-0 is time and axes-1,2 are spots in velocity field. Usually, this stack can be constracted by np.stack(u_list) and then reshape to flatten axes 1 and 2.
dt – time between two data points
mode – the averaging method, can be “direct” or “weighted”. “weighted” will use mean velocity as the averaging weight, whereas “direct” uses 1.

Returns

DataFrame of (corr, t)

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