Discrete cosine transform

DCT is a Fourier-related transform similar to the discrete Fourier transform (DFT), but using only real numbers. More information can be found here: https://en.wikipedia.org/wiki/Discrete_cosine_transform This code using DCT-I and DCT-III (inverce DCT) to extrapolate time data series and visualizes it with Highcharts ( https://www.highcharts.com/ )