The hyperparameters (which are stored in the vector 𝜽) have a remarkable impact on the recovery of DRT and impedance. To illustrate their influence, we applied the fGP-DRT method for specific values. We first set 𝜎 𝑓 = 𝜎 𝐿 = 1.0, 𝜎 𝑅 = 2.0, 𝜎 𝑛 = 0.5, and varied ℓ (10 -2 , 0.5, 1.0, and 2.0). The estimated DRT (with its credible bands included) and recovered impedance are given in the left and right panels of Figure , respectively. For ℓ = 10 -2 (Figure