def relative_difference(value_init, value_fit):

    """Calculate relative difference between two values.

        Parameter
        ---------
        value_init   :   float, reference value for error estimation 
        value_fit       :   float, values to identify relative difference to
        
        Return
        ------
        rel_diff       :   float between 0 and 100 relative difference between values in percent
    """
    
    rel_diff = abs((value_fit - value_init)/value_init) * 100    

    return rel_diff