Mathematics; oil prices; S&P 500; multivariate time series; Gaussian process model; vine copula; Bayesian variable selection; functional principal component analysis; nonlinear principal component analysis; Stock exchanges; Regression; Deep learning; Random variables; Principal components analysis; Forecasting; Modelling; Crude oil; Normal distribution; Securities markets; Multivariate analysis; Gaussian process; Mathematical models; Machine learning; Coronaviruses; Crude oil prices; Pricing; Internet stocks; Statistical methods; Time series; COVID-19; United States--US