Weighted HANTS SMOOTH — smooth

Weighted HANTS smoother

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

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)