model_start: Model starting parameters
In irg: Instantaneous Rate of Green Up

Description Usage Arguments Details Value See Also Examples

Try guessing starting parameters for model_params and model_ndvi.

1	model_start(DT, id = "id", year = "yr")

`DT`	filtered and scaled data.table of NDVI time series. Expects columns 'scaled' and 't' are present.
`id`	id column. default is 'id'. See details.
`year`	year column name. default is 'yr'.

The id argument is used to split between sampling units. This may be a point id, polygon id, pixel id, etc. depending on your analysis. This should match the id provided to filtering functions.

The input DT data.table appended with xmidS_start and xmidA_start columns. Note - we curently do not attempt to guess appropriate starting values for scalS and scalA.

Other model: model_ndvi(), model_params()

# Load data.table
library(data.table)

# Read in example data
ndvi <- fread(system.file("extdata", "sampled-ndvi-MODIS-MOD13Q1.csv", package = "irg"))

# Filter and scale NDVI time series
filter_ndvi(ndvi)
scale_doy(ndvi)
scale_ndvi(ndvi)

# Guess starting parameters for xmidS and xmidA
model_start(ndvi)