I want to divide the time series data into two subsets (upside and downside markets) using some statistical methods.
From the graph, it looks like
early 2004 to mid 2008 : upside
mid 2008 to early 2009 : downside
early 2009 to early 2011: upside
early 2011 to early 2012: downside
early 2012 to mid 2015: upside
mid 2015 to mid 2016: downside
mid 2016 to late 2017 : upside.
Is there any method to divide the dataset into two (upside and downside) in a logistic and systematic manner?