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Extrapolation techniques to fill gaps in movement data

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  • Extrapolation techniques to fill gaps in movement data

    Hello BIOMCH-L readers,

    I am working in gait biomechanics and am writing code to fill in missing
    data from streams of 3-dimensional co-ordinate data. Our system generates
    0 values in the co-ordinate file when a marker is out of camera-system
    view. Thus far I have tried polynomial curve fitting of varying orders
    based on datapoints prior to the missing value, and extrapolating the
    value. This method only met with limited success as the movement in
    different axes has behaviour of different (polynomial curve) orders. If
    the gap of missing markers is too large, the extrapolated point estimation
    diverges greatly, depending on the order of the polynomial fit.

    The second method I have tried is to fit a cubic spline to datapoints
    prior to the missing point in question. This is met with limited success.


    1. Most, if not all interpolation procedures that I know of require
    equally spaced data; thus if there is a gap in ones dataset, a polynomial
    curve or spline cannot be fit to the dataset! Could anyone confirm this

    2. I would like to know from individuals that use movement data (gait and
    others), what types of extrapolation or curve-fitting procedures are
    commonly being used.

    3. Does anyone know of a 3-dimensional spline technique whereby one can
    utilize all x,y,z co-ordinate data to extrapolate the next point(s)!

    I will post a follow-up with replies.


    Alan Morris
    Research Engineer - Gait Laboratory
    Bloorview MacMillan Centre
    350 Rumsey Road
    Toronto, Ontario
    Tel (416) 425-6220 x3508
    Fax (416) 425-1634

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