Histograms of the atmospheric parameters T_eff, log g, v_t, and [Fe/H] (upper panel) and their uncertainties (lower panel) for the complete PTPS sample of 885 stars with uniform spectroscopic analysis. The subsamples, as defined in Sect. 5, are colour coded. The blue area indicates dwarfs; the green line indicates subgiants; the brown line indicates giants; and the grey line indicates the whole sample.