Wrapper function for one step IRG calculation. Only defaults.
data.table of NDVI time series
Extended data.table 'irg' column of instantaneous rate of green-up calculated for each day of the year, for each individual and year.
data.table must have columns:
'id' - individual identifier
'yr' - year of observation
'NDVI' - NDVI value
'DayOfYear' - day of year/julian day of observation
'SummaryQA' - summary quality value for each sample (provided by MODIS)