“…This is in contrast to much of the concept/hybrid drift literature that deal with streams of data (often time series) that change over time (in one of the manners described above) and are typically from one source, such as environmental or energy data (Yang et al, 2019;Raza et al, 2019;Karnick et al, 2008;Ditzler et al, 2010), (i.e., f (X t ) and/or f (Y t |X t ) change over time). As such, many concept drift methods employ approaches that are inherently tailored to the temporal nature of the data streams, such as moving averages ( [Raza, et al, 2008]), detection systems to identify the presence ( [Yang, et al, 2019]) or speed ( [Minku, et al, 2009]) of a shift at a given instance, and ensemble methods that add, remove, or reweight classifiers across time ( [Raza, et al, 2008]; [Minku, et al, 2009]). While virtual drift work often does not assume changes over time, its methods usually center on reweighting observations ( [Sugiyama, et al, 2008]; ( [Shimodaira, 2000]) and assume that f (Y|X) remains constant between training and test sets.…”