smooth_wHANTS: Weighted HANTS SMOOTH

In phenofit: Extract Remote Sensing Vegetation Phenology

Weighted HANTS SMOOTH

Description

Weighted HANTS smoother

Usage

smooth_wHANTS(
  y,
  t,
  w,
  nf = 3,
  ylu,
  periodlen = 365,
  nptperyear,
  wFUN = wTSM,
  iters = 2,
  wmin = 0.1,
  ...
)

Arguments

y	Numeric vector, vegetation index time-series
t	Numeric vector, Date variable
w	(optional) Numeric vector, weights of y. If not specified, weights of all NA values will be wmin, the others will be 1.0.
nf	number of frequencies to be considered above the zero frequency
ylu	[low, high] of time-series y (curve fitting values are constrained in the range of ylu.
periodlen	length of the base period, measured in virtual samples (days, dekads, months, etc.). nptperyear in timesat.
nptperyear	Integer, number of images per year.
wFUN	weights updating function, can be one of 'wTSM', 'wChen' and 'wBisquare'.
iters	How many times curve fitting is implemented.
wmin	Double, minimum weigth (i.e. weight of snow, ice and cloud).
...	Additional parameters are passed to wFUN.

Value

• ws: weights of every iteration

• zs: curve fittings of every iteration

Author(s)

Wout Verhoef, NLR, Remote Sensing Dept. June 1998 Mohammad Abouali (2011), Converted to MATLAB Dongdong Kong (2018), introduced to R and modified into weighted model.

Examples

library(phenofit)
data("MOD13A1")
dt <- tidy_MOD13(MOD13A1$dt)
d <- dt[site == "AT-Neu", ]

l <- check_input(d$t, d$y, d$w, nptperyear=23)
r_wHANTS <- smooth_wHANTS(l$y, l$t, l$w, ylu = l$ylu, nptperyear = 23, iters = 2)

phenofit documentation built on Feb. 16, 2023, 6:21 p.m.