## 4 Results
### Data Characterisation: Main Findings  
The origin of the call was studied and Figure 1 presents the number of calls per district per 100,000 inhabitants. It can be observed that the great majority of calls are made from the greater Lisbon area (Lisbon and Setubal districts) with a number of calls between 2000 and 2500 per 100,000 inhabitants, followed by the the coastal districts north of Lisbon with values between 1500 and 2000 calls. In the mainland, 3 inland districts (Branganca, Guarda and Portalegre) use less the line, with a number of calls ranging 500 and 1000 per 100,000 inhabitants. The citizens living in the islands (Azores and Madeira autonomous regions) use the phone line even less; one possible explanation for this minor use of the SNS24 phone line is the existence of a similar service run by the regional health authorities. One important and needed data characterisation is the clinical pathway, being it the attribute the classification models will aim to predict (known as target class). The proportion of examples of each clinical pathway on the dataset is presented in Figure 2. As can be observed, the dataset is very unbalanced, which turns the learning of a classification model a more complex problem (the absolute numbers are presented in Table A1 on Appendix A). The most frequent pathway is \"Cough\" with 10.68% of the calls, followed by \"Nausea and vomiting problems\", \"Abdominal pain\", \"Oropharynx problem\" and \"Rash\" with 7.44%, 6.26%, 5.08% and 4.86%, respectively. Moreover, the 23 most frequent pathways account for at least 80% of the calls, with the 7 most frequent ones accounting for around 42.4%; furthermore, there are 25 pathways for which the frequency is less than 1%. Regarding the caller, Figure 3 shows that about half of the calls is to report a problem of the callers themselves, followed by calls from the mother of the patient (26%); father or husband of the patient account for 5% each, whereas caretakers account for 1% of the callers. Concerning the citizen gender distribution, the majority is female representing 59% of the calls. For the age distribution it can be observed that the phone line is mostly used to attend patients in their first years (up to five years old), followed by young adults, with the number decreasing for the elderly; this trend is presented in Figure 4.  
Figure 1: Total number of calls per district per 100,000 inhabitants (image generated using [[https://paintmaps.com/](https://paintmaps.com/)]([https://paintmaps.com/](https://paintmaps.com/)), accessed on 9 November 2022). Figure 2: Distribution of calls per clinical pathway. A similar age distribution analysis was done for the 10 most common pathways; these were then empirically clustered by similar trends over patient age, having one cluster following the general trend and 3 others with some differences. The distribution for those clustered pathways can be observed in Figure 5. The first cluster (top-left) follows the general trend and includes four pathways: \"Cough\", \"Nausea and vomiting problems\", \"Rash\" and \"Diarrhea\"; the second cluster (top-right), shows the age distribution for the \"Flu Syndrome\": younger patients are not so frequent, with an increased percentage for the adults between 30 and 40 years old. \"Chest pain\" and \"Migraine\" pathways represent the third cluster (bottom-left) and have the most dissimilar distribution when compared to the general age distribution. The final cluster (bottom-right) includes \"Abdominal pain\", \"Oropharynx problem\" and \"Uninary problem\" pathways and follow, somehow in a smoother version, the general trend. Figure 4: Distribution of calls per the age of the citizen. Figure 3: Distribution of calls by relation of the caller to the citizen. A study of the distribution of calls over time, namely hour of the day, day of the week and month of the year was also made. Figure 6 presents the results (on top, the hour of the day; on bottom left and right, the day of the week and month of the year, respectively.