
This function smoothes signals with a finite difference penalty of order 2.
This function is modified from ptw
package.
whit2(y, lambda, w = rep(1, ny))
signal to be smoothed: a vector
smoothing parameter: larger values lead to more smoothing
weights: a vector of same length as y. Default weights are equal to one
A numeric vector, smoothed signal.
Eilers, P.H.C. (2004) "Parametric Time Warping", Analytical Chemistry, 76 (2), 404 -- 411.
Eilers, P.H.C. (2003) "A perfect smoother", Analytical Chemistry, 75, 3631 -- 3636.
# NOT RUN {
library(phenofit)
data("MOD13A1")
dt <- tidy_MOD13.gee(MOD13A1$dt)
y <- dt[site == "AT-Neu", ][1:120, y]
plot(y, type = "b")
lines(whit2(y, lambda = 2), col = 2)
lines(whit2(y, lambda = 10), col = 3)
lines(whit2(y, lambda = 100), col = 4)
legend("bottomleft", paste("lambda = ", c(2, 10, 15)), col = 2:4, lty = rep(1, 3))
# }
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