Global azimuthal asymmetry in oxygen abundance distribution across the whole disc of each target galaxy and control galaxy (M-12078-12705). The lines and symbols show the absolute value of difference between the arithmetic means of the deviations from the O/H – R relation for the spaxels within the sector, with azimuthal angles from φ to φ + 180 and from φ + 180 to φ + 360 as a function of angle φ.