latent Dirichlet allocation method-based nowcasting approach for prediction of silver price

Silver is a metal that offers significant value to both investors and companies. The purpose of this study is to make an estimation of the price of silver. While making this estimation, it is planned to include the frequency of searches on Google Trends for the words that affect the silver price. Thus, it is aimed to obtain a more accurate estimate. First, using the Latent Dirichlet Allocation method, the keywords to be analyzed in Google Trends were collected from various articles on the Internet. Mining data from Google Trends combined with the information obtained by LDA is the new approach this study took, to predict the price of silver. No study has been found in the literature that has adopted this approach to estimate the price of silver. The estimation was carried out with Random Forest Regression, Gaussian Process Regression, Support Vector Machine, Regression Trees and Artificial Neural Networks methods. In addition, ARIMA, which is one of the traditional methods that is widely used in time series analysis, was also used to benchmark the accuracy of the methodology. The best MSE ratio was obtained as 0,000227131 ± 0.0000235205 by the Regression Trees method. This score indicates that it would be a valid technique to estimate the price of "Silver" by using Google Trends data using the LDA method

Detecting anomalies in wholesale electricity day-ahead market bidding data using LSTM-network

In this thesis it is studied how neural networks can be used for anomaly detection in day-ahead wholesale electricity market trading data. Economics of electricity markets lays a foundation on detecting distinctive patterns in supply behavior reflecting market manipulation, such as economic and physical withholding of production capacity. The impact of market abusive supply behavior is studied on shapes of supply curves. A neural network model is used to provide score to measure stationarity of bidding behavior. An unsupervised machine learning framework for anomaly detection is set up by using a rolling window approach. 24 hours of high dimensional supply trading data is used as input to make prediction one hour ahead. Prediction errors of every individual hour are used as a time series of anomaly score, which is thoroughly analyzed in the light of signs of market manipulation based to the literature of electricity market economics. The study is conducted on two years of anonymous aggregated day-ahead trading data collected by The European Union Agency for Cooperation of Energy Regulators received from Energy Authority of Finland. Idea is to fit neural network to the data to estimate how supply curve of an hour would look like conditional on 24 previous hours and external variables. Neural networks are used for the estimation as they are capable of modelling non-linear spatial dependencies in the data. LSTM model is further chosen because it is designed to handle long term dependencies in the data. If the prediction errors are low enough on average, it can be assumed that the model can capture stationary behavior in the data and outliers can be assumed to result from changes in data generation process. If model can predict supply curves well enough on average, large prediction errors can indicate that something unexpected has happened in the markets. LSTM-model is trained to make rolling window predictions using 5-fold walk forward validation approach, where chronological order of the data is maintained to mimic real life prediction scenario. Early stopping is used to prevent overfitting. Hyperparameters are chosen via grid search likewise using 5-fold walk forward validation. Two major distinctive types of supply behavior are identified from the literature, economic withholding and physical withholding. Their impact is studied on supply curves and is paid attention in the analysis of anomaly score. Mean absolute error of individual hour is chosen for anomaly score, which is referred as h-MAE. Performance of the model is compared to one used by Guo et al. (2021) in similar function of predicting supply curves. Method is promising in detecting out-of-ordinary supply curves, based on thorough statistical survey of the results and brief qualitative survey, in which a confirmed market violation was detected, as well as erroneous period in the data. Linking market manipulation to the anomaly score directly proves difficult. However, the method offers a noteworthy possibility to surveil and study supply curves in day-ahead market as it benefits from enormous amount of high-dimensional data and is capable to take account the spatial and temporal non-linear relations of the supply curves. This Master’s thesis was done in affiliation with Energy Authority of Finland

Contribution to Financial Modeling and Financial Forecasting

This thesis consists of three chapters. Each chapter is independent research that is conducted during my study. This research is concentrated on financial time series modeling and forecasting. On first chapter, the research aims to prove that any abnormal behavior in debt level is a signal of future unexpected return for firms that is listed in indexes in this study, hence it is a signal to buy. In order to prove this theory multiple indexes from around the world were taken into consideration. This behavior is consistent in most of indexes around the word. The second chapter investigate the effect of United State president speech on value of United State Currency in Foreign Exchange Rate market. In this analysis it is shown that during the time the president is delivering a speech there is distinctive changes in USD value and volatility in global markets. This chapter implies that this effect cannot be captured by linear models, and the impact of the presidential speech is short term. Finally, the third chapter which is the major research of this thesis, suggest two new methods that potentially enhance the financial time series forecasting. Firstly, the new ARMA-RNN model is presented. The suggested model is inheriting the process of Autoregressive Moving Average model which is extensively studied, and train a recurrent neural network based on it to benefit from unique ability of ARMA model as well as strength and nonlinearity of artificial neural network. Secondly the research investigates the use of different frequency of data for input layer to predict the same data on output layer. In other words, artificial neural networks are trained on higher frequency data to predict lower frequency. Finally, both stated method is combined to achieve more superior predictive model

From metaheuristics to learnheuristics: Applications to logistics, finance, and computing

Un gran nombre de processos de presa de decisions en sectors estratègics com el transport i la producció representen problemes NP-difícils. Sovint, aquests processos es caracteritzen per alts nivells d'incertesa i dinamisme. Les metaheurístiques són mètodes populars per a resoldre problemes d'optimització difícils en temps de càlcul raonables. No obstant això, sovint assumeixen que els inputs, les funcions objectiu, i les restriccions són deterministes i conegudes. Aquests constitueixen supòsits forts que obliguen a treballar amb problemes simplificats. Com a conseqüència, les solucions poden conduir a resultats pobres. Les simheurístiques integren la simulació a les metaheurístiques per resoldre problemes estocàstics d'una manera natural. Anàlogament, les learnheurístiques combinen l'estadística amb les metaheurístiques per fer front a problemes en entorns dinàmics, en què els inputs poden dependre de l'estructura de la solució. En aquest context, les principals contribucions d'aquesta tesi són: el disseny de les learnheurístiques, una classificació dels treballs que combinen l'estadística / l'aprenentatge automàtic i les metaheurístiques, i diverses aplicacions en transport, producció, finances i computació.Un gran número de procesos de toma de decisiones en sectores estratégicos como el transporte y la producción representan problemas NP-difíciles. Frecuentemente, estos problemas se caracterizan por altos niveles de incertidumbre y dinamismo. Las metaheurísticas son métodos populares para resolver problemas difíciles de optimización de manera rápida. Sin embargo, suelen asumir que los inputs, las funciones objetivo y las restricciones son deterministas y se conocen de antemano. Estas fuertes suposiciones conducen a trabajar con problemas simplificados. Como consecuencia, las soluciones obtenidas pueden tener un pobre rendimiento. Las simheurísticas integran simulación en metaheurísticas para resolver problemas estocásticos de una manera natural. De manera similar, las learnheurísticas combinan aprendizaje estadístico y metaheurísticas para abordar problemas en entornos dinámicos, donde los inputs pueden depender de la estructura de la solución. En este contexto, las principales aportaciones de esta tesis son: el diseño de las learnheurísticas, una clasificación de trabajos que combinan estadística / aprendizaje automático y metaheurísticas, y varias aplicaciones en transporte, producción, finanzas y computación.A large number of decision-making processes in strategic sectors such as transport and production involve NP-hard problems, which are frequently characterized by high levels of uncertainty and dynamism. Metaheuristics have become the predominant method for solving challenging optimization problems in reasonable computing times. However, they frequently assume that inputs, objective functions and constraints are deterministic and known in advance. These strong assumptions lead to work on oversimplified problems, and the solutions may demonstrate poor performance when implemented. Simheuristics, in turn, integrate simulation into metaheuristics as a way to naturally solve stochastic problems, and, in a similar fashion, learnheuristics combine statistical learning and metaheuristics to tackle problems in dynamic environments, where inputs may depend on the structure of the solution. The main contributions of this thesis include (i) a design for learnheuristics; (ii) a classification of works that hybridize statistical and machine learning and metaheuristics; and (iii) several applications for the fields of transport, production, finance and computing