def autodec(fwhm):
    """
    Automatically calculates the appropriate decimal place to track based on a full-width-at-half-maximum

    :param fwhm: full-width-at-half-maximum
    :return: decimal power
    :rtype: int
    """
    shift = fwhm
    n = 0
    while shift < 1.:
        n += 1
        shift = fwhm * 10 ** n
    return n + 1