# A Modified Bayesian Network Model to Predict Reorder Level of Printed Circuit Board
## Variables Specification and Data Preprocessing  
### Variables Specification  
Reorder level related variables were inherited and derived from fields in enterprise resource plan (ERP) system and order management system (OMS) in which the same type of repeated orders placed at different date are labeled with the same production number but different order numbers generated by the manufacturer's coding rule. On this basis, statistics of delivery area, quantity, transaction money, and interval days of the past 30 months before a set date were derived and the related description is presented in Table 1. The set date is prepared for orders selection and batch production. The statistic excludes the accumulation before 30 months under the consideration of order's lifecycle based on expert experience. The reorder level is the classification objective and four levels are set based on the reorder frequency of a production number in the next six months after a set date. Data from three factories accumulated in ERP and OMS of Fastprint were collected and integrated. Then 33,542 training samples were selected randomly with the set date 31 March 2016 based on the \begin{table}
\begin{tabular}{c c c} \hline \hline
**Variables** & **Symbols** & **Description** \\ \hline \multirow{2}{*}{Layer number} & \multirow{2}{*}{_Ln_} & PCB is made of resin, substrate, and \\  & & copper foil and the Ln is the number of \\  & & copper foil layers. \\ \hline \multirow{2}{*}{Continued days} & \multirow{2}{*}{_Condays_} & Interval days between the first order date \\  & & and a set date. \\ \hline \multirow{2}{*}{Recency} & \multirow{2}{*}{_Rec_} & A period between the last order date and \\  & & a set date. \\ \hline \multirow{2}{*}{Maximum/minimum/mean of  delivery interval days} & \multirow{2}{*}{_Delind\_Max/Min/Mean_} & Days between order date and required \\  & & delivery date in the past 30 months. \\ \hline \multirow{2}{*}{Maximum/minimum/mean of  interval days} & \multirow{2}{*}{_Interval\_Max/Min/Mean_} & Days between two adjacent order dates in \\  & & the past 30 months. \\ \hline \multirow{2}{*}{Frequency in 30 months} & \multirow{2}{*}{_Fra_3} & Reorder frequency within 30 months \\  & & before a set date. \\ \hline \multirow{2}{*}{Frequency} & \multirow{2}{*}{_Fre_} & Reorder frequency before a set date. \\  & & \\ \hline \multirow{2}{*}{Maximum/minimum/mean/sum  of delivery area (m\({}^{2}\))} & \multirow{2}{*}{_Area\_Max/Min/Mean/Sum_} & Delivery area of the past 30 months \\  & & a set date. \\ \hline \multirow{2}{*}{Maximum/minimum/mean/sum  of money (CNT)} & \multirow{2}{*}{_Mon\_Max/Min/Mean/Sum_} & Transaction money of the past 30 months \\  & & before a set date. \\ \hline \multirow{2}{*}{Maximum/minimum/mean/sum  of delivery quantity} & \multirow{2}{*}{_Quun\_Max/Min/Mean/Sum_} & Delivery quantity of the past 30 months \\  & & before a set date. \\ \hline \multirow{2}{*}{Reorder level} & \multirow{2}{*}{_Rel_} & 1, 2, 3, and 4 levels corresponding to the \\  & & reorder frequency 0, 1–2, 3–5, and \textgreater{}5 \\ \multicolumn{2}{c}{} & within six months, respectively. \\ \hline \end{tabular} Note: Statistic parameters of maximum/minimum/mean/sum were derived from the orders with the same production number accumulated in the past 30 months before a set date.  
\end{table} 
Table 1: Variable specification. orders accumulated between 1 October 2013 and 31 March 2016. Meanwhile 14,484 test samples with another set date of 31 May 2016 were selected randomly based on the orders accumulated between 1 December 2013 and 31 May 2016 excluding the records with the same production number in training samples. The observed reorder levels for the records from training and test samples are transformed from the reorder frequency within six months after its set date (i.e., the frequency accumulated between 1 April 2016 and 30 September 2016 for training samples and between 1 June 2016 and 31 October 2016 for test samples). Each record was aggregated based on the orders placed during the past 30 months according to the production number.