Generating phase dummies for turning points

[TomDoan]

If you have two series of dummy variable "turning points", you can generate dummies for the phases using a calculation like the following:

local real peak0 trough0
sstats(min) startl endl %if(peak,t,%na)>>peak0 %if(trough,t,%na)>>trough0
if %defined(up)
   set(first=peak0<trough0) up   startl endl = up{1}-peak{1}+trough{1}
if %defined(down)
   set(first=peak0>trough0) down startl endl = down{1}-trough{1}+peak{1}

The SSTATS is used to determine which phase the process is in at the start by determining which turning point is hit first. If it's a peak, then the process is starting in an up phase and if it's a trough, it's starting in a down phase.