def replace_missing(value, missing=0.0):
    """Returns missing code if passed value is missing, or the passed value if it is not missing; a missing value in the EDF contains only a period, no numbers; NOTE: this function is for gaze position values only, NOT for pupil size, as missing pupil size data is coded '0.0'

	Parameters
	----------
	value : str
		Either an X or a Y gaze position value (NOT pupil size! This is coded '0.0')
	missing : float
		The missing code to replace missing data with (default = 0.0)

	Returns
	-------
	float
		Either a missing code, or a float value of the gaze position

	"""
    if value.replace(' ', '') == '.':
        return missing
    else:
        return float(value)
