runScymCore: Run SCYM core: basic 2-window SCYM function based on US maize...
In LobellLab/SCYMr:

Function intended to be applied by row to a df of points + attributes

1 2	runScymCore(days, vi1, vi2, p_hinge, v_hinge, Augtmax, JJA_radn, apsimtable = ctable)

`days`	column name for character vector denoting observation days for both windows in format '180_210'
`vi1`	column name for vi observation in window 1
`vi2`	column name for vi observation in window 2
`p_hinge`	column name for precip hinge value
`v_hinge`	column name for vpd hinge value
`Augtmax`	column name for augmaxt
`apsimtable`	data.frame with coefficient table to use

# to apply to data frame using purrr (better than rowwise, etc)
ls2017_yield <- ls2017 %>%
  mutate(biomass_scymr = pmap_dbl(list(days = Dates, vi1 = gcvi1, vi2 = gcvi2,
                                       p_hinge=phinge, v_hinge=vhinge,
                                       Augtmax = Augmaxt, JJA_radn = JJAradn),
                                       .f = runScymCore, apsimtable = ctable),
         yield_SCYMr_tha = biomass_scymr * 0.45)