Effects of the hyperparameters on the model predictions (attenuation per parsec) in region 1 with σ = 0.1. Red points are the true values and black points with blue error bars are predictions by the model. It is important to note that the predicted uncertainties are highly correlated. Each column is for different values of λ (length scale), and each row is for different values of θ. The number in the top left corner is the natural logarithm of the reconstruction probability, defined by Eq. (18).