High frequency surrogate method

This function splits the vGRF into its HiF (>=10 Hz) and LoF (0Hz to < 10 Hz) components.

This function finds the peak in the HiF signal and outputs a figure and two values. The figure plots the vGRF, HiF and LoF signals and demonstrates visually the occurrence of the peak HiF signal. The HiF_locs output is the frame number of the peak in the HiF signal. The HiF_on_Fz output is the magnitude of the vGRF signal at HiF_locs. This function requires two inputs; 1) a filtered vGRF signal (in column form) and 2) the sampling frequency (Fs).
This method is based on the following publication.

Blackmore, T., Willy, R.W., Creaby, M.W., 2016. The high frequency component of the vertical ground reaction force is a valid surrogate measure of the impact peak. J. Biomech. 49(3): 479-83, https://www.ncbi.nlm.nih.gov/pubmed/26783094.