v_curve: v_curve

In phenofit: Extract Remote Sensing Vegetation Phenology

Description

V-curve is used to optimize Whittaker parameter lambda. Update 20180605 add weights updating to whittaker lambda selecting

Usage

v_curve(INPUT, lg_lambdas, d = 2, IsPlot = FALSE, wFUN = wTSM, iters = 2)

Arguments

INPUT	A list object with the elements of t, y, w, Tn (optional) and ylu, returned by check_input().
lg_lambdas	lg lambda vectors of Whittaker parameter.
d	Difference order.
IsPlot	Boolean. Whether to plot figure?
wFUN	weights updating function, can be one of wTSM(), wChen(), wBisquare() and wSELF().
iters	How many times curve fitting is implemented.

Examples

library(phenofit)
data("MOD13A1")

dt <- tidy_MOD13.gee(MOD13A1$dt)
st <- MOD13A1$st

sitename <- dt$site[1]
d     <- dt[site == sitename, ] # get the first site data
sp    <- st[site == sitename, ] # station point
# global parameter
IsPlot = TRUE
nptperyear = 23

dnew     <- add_HeadTail(d, nptperyear = nptperyear) # add one year in head and tail
INPUT    <- check_input(dnew$t, dnew$y, dnew$w, nptperyear, 
                        maxgap = nptperyear/4, alpha = 0.02, wmin = 0.2)
# INPUT$y0 <- dnew$y   # raw time-series, for visualization

lg_lambdas <- seq(0, 3, 0.1)
r <- v_curve(INPUT, lg_lambdas, d = 2, IsPlot = TRUE)

phenofit documentation built on April 2, 2020, 5:07 p.m.