Calculate growth rate and LAI at t0

Usage

calc_r_x0(param_r, min_r = 0.02, max_r = 0.05, k = 6)

Arguments

param_r: Output of the function read_sb_growth_parameter, which produces a list containing the LAI images and the associated dates
min_r: minimum growth rate for sugar beet. Default min_r is fixed to 0.02 to ensure that the growth rate at the inflection point of the sigmoid is at least 1 unit of LAI per month.
max_r: maximum growth rate for sugar beet. Default max_r is fixed to 0.05 to ensure that the growth rate at the inflection point of the sigmoid is at most 2.5 units of LAI per month.
k: carrying capacity, which is the maximum LAI that can be attained. This value can be cultivar-dependent. The default is fixed to 6

Value

param_rxt: list containing parameters that are necessary to calculate c_closure. These parameters are r, the growth rate, x0, the initial LAI value, and t0, the initial date.

Details

Fits a non-linear model to remotely sensed LAI values and estimates the leaf area index (LAI) and growth rate r at the start of the time window t0.

Examples

img_dir <- system.file("extdata", "uav_img",package = "cercospoRa")
epidemic_onset_param <-
  read_sb_growth_parameter(img_files = list.files(img_dir,pattern = "tif",
                                                  full.names = TRUE),
                           img_dates = as.POSIXct(
                             c("2022-06-14","2022-06-28"),tz = "UTC"),
                           target_res = 10)
param_rxt <- calc_r_x0(epidemic_onset_param,
                       min_r = 0.02,
                       max_r = 0.05,
                       k = 6)