Evolution of the R² performance of the Random Forest predictors (for translucent gas) when adding noise of constant variance to all line intensities, as a function of the noise level σ_noise, for the 3 best tracers for translucent medium (C₂H(1–0)/HCN(1–0), C₂ H(1–0)/¹³CO(1–0), and C₂ H(1–0)/C¹⁸O(1–0)) and for the four tracers least affected by the noise (¹³CO(1–0)/C¹⁸O(1–0), C¹⁸O(1–0)/CF⁺(1–0), ¹³CO(1–0)/CF⁺(1–0), and HCN/CF⁺(1–0)).