Filtering of Time Series
	q Time filtering technique is used to remove or to retain variations at particular bands of frequencies from the time series. q There are three types of filtering: (1) High-Pass Filtering       keep high-frequency parts of the variations and remove low- frequency parts of the variations. (2) Low-Pass Filtering       keep low-frequency and remove high-frequency parts of the variations. (3) Band-Pass Filtering      remove both higher and lower frequencies and keep only certain frequency bands of the variations.