as defined in Basler et al. 2016 (Agr. For. Meteorlogy)
LIN(par, data, spring = c(60, 151))
a vector of parameter values, this is functions specific
input data (see reference for detailed description), data should be formatted using flat_format()
a vector defining spring as a couple of DOY values default is March, April, May or DOY 60 - 151
raster or vector with estimated phenophase timing (in DOY)
if (FALSE) {
estimate <- LIN(data = data, par = par)
}