Weighted Savitzky-Golay

Source: R/smooth_wSG.R

Weighted Savitzky-Golay

smooth_wSG(
  y,
  w,
  nptperyear,
  ylu,
  wFUN = wTSM,
  iters = 2,
  frame = floor(nptperyear/7) * 2 + 1,
  d = 2,
  ...
)

Arguments

y

Numeric vector, vegetation index time-series
w

(optional) Numeric vector, weights of y. If not specified, weights of all NA values will be wmin, the others will be 1.0.
nptperyear

Integer, number of images per year.
ylu

(optional) [low, high] value of time-series y (curve fitting values are constrained in the range of ylu.
wFUN

weights updating function, can be one of 'wTSM', 'wChen' and 'wBisquare'.
iters

How many times curve fitting is implemented.
frame

Savitzky-Golay windows size
d

polynomial of degree. When d = 1, it becomes moving average.
...

Additional parameters are passed to wFUN.

Value

  • ws: weights of every iteration

  • zs: curve fittings of every iteration

References

  1. Chen, J., J\"onsson, P., Tamura, M., Gu, Z., Matsushita, B., Eklundh, L., 2004. A simple method for reconstructing a high-quality NDVI time-series data set based on the Savitzky-Golay filter. Remote Sens. Environ. 91, 332-344. https://doi.org/10.1016/j.rse.2004.03.014.

  2. https://en.wikipedia.org/wiki/Savitzky%E2%80%93Golay_filter

Examples

library(phenofit)

#> Error in library(phenofit): there is no package called ‘phenofit’
data("MOD13A1")

#> Warning: data set ‘MOD13A1’ not found
dt <- tidy_MOD13(MOD13A1$dt)

#> Error in tidy_MOD13(MOD13A1$dt): object 'MOD13A1' not found
d <- dt[site == "AT-Neu", ]

#> Error in eval(expr, envir, enclos): object 'site' not found

l <- check_input(d$t, d$y, d$w, nptperyear=23)

#> Error in check_input(d$t, d$y, d$w, nptperyear = 23): object 'd' not found
r_wSG <- smooth_wSG(l$y, l$w, l$ylu, nptperyear = 23, iters = 2)

#> Error in smooth_wSG(l$y, l$w, l$ylu, nptperyear = 23, iters = 2): object 'l' not found