## 4 Methodology
### Feature Creation
\begin{table}
\begin{tabular}{c c c c c} \hline
**Features Group (FG)** & **FG ID** & **Feature** & **Description** & **Type** \\ \hline \multirow{4}{*}{Sensor reading values} & \multirow{2}{*}{1} & \multirow{2}{*}{P1} & Pressure measurement from & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & & sensor P1 & \\ \cline{5-5}  & & & T2 &
\begin{tabular}{} \end{tabular} & \multirow{2}{*}{Real number} \\ \hline \multirow{4}{*}{Expected mixture vapor saturation pressure for temperature T2} & \multirow{4}{*}{2} & spt002 & Mixture \#1 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & spt0 & Mixture \#2 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & spt1 & Mixture \#3 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & spt2 & Mixture \#4 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & spt3 & Mixture \#5 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & spt4 & Mixture \#6 & \multirow{2}{*}{Real number} \\ \hline \multirow{4}{*}{Pressure P1 in range} & \multirow{4}{*}{3} & \multirow{2}{*}{\(p<7.06\)} & Pressure below 7.06 kg/cm\({}^{2}\) & \multirow{2}{*}{Boolean} \\ \cline{5-5}  & & & \(p<7.14\) & Pressure below 7.14 kg/cm\({}^{2}\) & \multirow{2}{*}{Boolean} \\ \cline{5-5}  & & & \(p>7.63\) & Pressure above 7.63 kg/cm\({}^{2}\) & \multirow{2}{*}{Boolean} \\ \hline \multirow{4}{*}{Expected T1 temperature for mixture} & \multirow{4}{*}{4} & T1-spt1 & Mixture \#3 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & T1-spt2 & Mixture \#4 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & T1-spt3 & Mixture \#5 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & T1-spt4 & Mixture \#6 & \multirow{2}{*}{Real number} \\ \hline \multirow{4}{*}{Relative pressure, comparing pressure P1 and expected mixture pressure for temperature T2.} & \multirow{4}{*}{5} & spr002 & spt002/P1 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & spr0 & spt1/P1 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & spr1 & spt2/P1 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & spr2 & spt3/P1 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & spr3 & spt4/P1 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & spr4 & spt5/P1 & \multirow{2}{*}{Real number} \\ \hline \multirow{4}{*}{Ratio between estimated T1 temperature for mixture, and the P1 pressure.} & \multirow{4}{*}{6} & T1/P1-spt1-T2 & Mixture \#3 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & T1/P1-spt2-T2 & Mixture \#4 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & T1/P1-spt3-T2 & Mixture \#5 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & T1/P1-spt4-T2 & Mixture \#6 & \multirow{2}{*}{Real number} \\ \cline{5-5}  & & T1/P1-spt1.vref & Mixture \#3 & \multirow{2}{*}{Boolean} \\ \cline{5-5}  & & T1/P1-spt2.vref & Mixture \#4 & \multirow{2}{*}{Boolean} \\ \cline{5-5}  & & T1/P1-spt3.vref & Mixture \#5 & \multirow{2}{*}{Boolean} \\ \cline{5-5}  & & T1/P1-spt4.vref & Mixture \#6 & \multirow{2}{*}{Boolean} \\ \hline \end{tabular}
\end{table} 
Table 3: Some of the features we created for the machine learning models. _spr_ abbreviates _saturation pressure ratio_, while _spt_ abbreviates _saturation pressure total_. Figure 5: Feature correlation for ten selected features in each case, when forecasting the amount of C5 present in distilled LPG at the end of the distillation process in the debutanizer columns, for Unit A. On (**A**) we present feature correlations for Experiment 1, while on (**B**) we present feature correlations for Experiment 2. Figure 6: Feature correlation for ten selected features in each case, when forecasting the amount of C5 present in distilled LPG at the end of the distillation process in the debutanizer columns, for Unit B. On (**A**) we present feature correlations for Experiment 1, while on (**B**) we present feature correlations for Experiment 2. Figure 7: Feature correlation for ten selected features in each case, when forecasting if the amount of C5 present in distilled LPG at the end of the distillation process in the debutanizer columns remains within the required specification thresholds, for _Unit A_.