Distribution of sampled data column normalised by sum (left), model colour-coded by the probability density function (centre), and the normalised residual (right) in the [M/H]−v_ϕ plane (azimuthal velocity vs metallicity) for high-α evolving means model. The flat distribution of red stars at higher metallicities in the residuals show that the model is not able to fit the non-Gaussianity (long tail towards lower velocities) of the high-α disc. The systematic scatter in the periphery is due to random error in the data. However, for [M/H]<−0.7, the lack of strong systematic patterns, the low-amplitude, and the small scatter of the residuals in the central regions (with the major bulk of the data) verifies the validity of the model. The median, 16th and 84th percentile tracks for our data are shown in black lines to guide the eye towards the bulk of the data.