The development of a housing prices prediction model can assist a house seller or a real estate agent to make better-informed decisions based on house price valuation. Only a few works report the use of machine learning (ML) algorithms to predict the values of properties in Brazil. This study analyzes a dataset composed of 12,223,582 housing advertisements, collected from Brazilian websites from 2015 to 2018. Each instance comprises twenty-four features of five different data types: integer, date, string, float, and image. To predict the property prices, we ensemble two different ML architectures, based on Random Forest (RF) and Recurrent Neural Networks (RNN). This study demonstrates that enriching the dataset and combining different ML approaches can be a better alternative for prediction of housing prices in Brazil.

In machine learning, one must acquire labels to help supervise a model that will be able to generalize to unseen data. However, the labeling process can be tedious, long, costly, and error-prone. It is often the case that most of our data is unlabeled. Semi-supervised learning (SSL) alleviates that by making strong assumptions about the relation between the labels and the input data distribution. This paradigm has been successful in practice, but most SSL algorithms end up fully trusting the few available labels. In real life, both humans and automated systems are prone to mistakes; it is essential that our algorithms are able to work with labels that are both few and also unreliable. Our work aims to perform an extensive empirical evaluation of existing graph-based semi-supervised algorithms, like Gaussian Fields and Harmonic Functions, Local and Global Consistency, Laplacian Eigenmaps, Graph Transduction Through Alternating Minimization. To do that, we compare the accuracy of classifiers while varying the amount of labeled data and label noise for many different samples. Our results show that, if the dataset is consistent with SSL assumptions, we are able to detect the noisiest instances, although this gets harder when the number of available labels decreases. Also, the Laplacian Eigenmaps algorithm performed better than label propagation when the data came from high-dimensional clusters. CCS CONCEPTS • Computing methodologies → Artificial intelligence; Machine learning;

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No problema do caixeiro viajante (TSP), o objetivo é encontrar uma rota que passe por todas as cidades e retorne à cidade de origem com a menor distância total percorrida. Como um problema NP-completo, encontrar soluções não é fácil, e várias heurísticas foram propostas. Atualmente, com o avanço no uso do Aprendizado de Máquina (AM), é possível usar o AM para prever conexões entre cidades na solução ótima. Nosso modelo, baseado em redes neurais de grafos, obteve uma pontuação F1 de 0,10645 na tabela de classificação pública do KDD-BR 2021, o suficiente para superar a solução gulosa. Isso mostra que o AM pode ser uma boa técnica para gerar soluções mais rapidamente ou até mesmo construir soluções melhores.