define the location of peaks and troughs
define_recession(peak,trough)
peak = 0 if a peak does not not belong to the recession phase
trough = 0 if a trough does not not belong to the recession phase
nothing: data are saved in the database: GROCERDIR+'/macros/grocer/db/define_recession.dat'
define_recession(0,1) // Gives the default values provided with the installation package: the peak is supposed not to belong to the recession period and the trough to belong to it. define_recession(1,0) // Gives exactly the contrary (peak belonging to the recession period and the trough not).