Correlations in the [Ca/Fe] and [Ca/H] excess distributions of the Galactic disc for samples A and C. Upper panel: pixel-to-pixel (black dots) diagram showing the [Ca/Fe] excess variation in sample C as a function of sample A. The blue contours show the distribution of the [Ca/Fe] excess of sample C vs. that of sample A and encloses fractions of 90, 75, 60, 45, 30, and 20% of the total number of pixels. The red line shows a linear fit to the black dots. Bottom panel: same as the upper panel for the [Ca/H] excess case.