absdif ( p0,  p1 )

Calculate "Rotational" difference between two positions in radians.

equal (
        p0,
        p1,
        crit=1.e-4,
        )

Are the two positions identical?

fromheader (
        h,
        fraction,
        hardware=None,
        )

Calculate goniostat position at fraction of the scan

Will raise AttributeError if there is no scan info in the header.