The amplitude of morphological lopsidedness  ⟨ A₁ ⟩  averaged over large radii vs. the tidal parameter T_p (large filled triangles). In some cases, up to two companions could not be included in the calculation of T_p because of a lack of data. This gives a lower limit to T_p (large open triangles). In two cases, the H i emission could only be detected within R₂₅ so that  ⟨ A₁ ⟩  averaged over small radii is plotted vs. T_p (small open triangles). For all galaxies which have no known companions, a tidal parameter of  − 10 is assumed. There is no clear correlation of the lopsided amplitude with the tidal parameter.