as defined in Basler et al. 2016 (Agr. For. Meteorlogy)
SM1(par, data)
a vector of parameter values, this is functions specific
input data (see reference for detailed description), data should be formatted using flat_format()
raster or vector with estimated phenophase timing (in DOY)
if (FALSE) {
estimate <- SM1(data = data, par = par)
}