sg.smooth: Savitzky-Golay smoothing filter

In jeffreyevans/spatialEco: Spatial Analysis and Modelling Utilities

Savitzky-Golay smoothing filter

Description

Smoothing of time-series data using Savitzky-Golay convolution smoothing

Usage

sg.smooth(x, f = 4, l = 51, d = 1, na.rm, ...)

Arguments

x	A vector to be smoothed
f	Filter type (default 4 for quartic, specify 2 for quadratic)
l	Convolution filter length, must be odd number (default 51). Defines degree of smoothing
d	First derivative (default 1)
na.rm	NA behavior
...	not used

Value

A vector of the smoothed data equal to length of x. Please note; NA values are retained

Author(s)

Jeffrey S. Evans <jeffrey_evans<at>tnc.org>

References

Savitzky, A., and Golay, M.J.E. (1964). Smoothing and Differentiation of Data by Simplified Least Squares Procedures. Analytical Chemistry. 36(8):1627-39

Examples

y <- c(0.112220988, 0.055554941, 0.013333187, 0.055554941, 0.063332640, 0.014444285, 
       0.015555384, 0.057777140, 0.059999339, 0.034444068, 0.058888242, 0.136665165, 
       0.038888458, 0.096665606,0.141109571, 0.015555384, 0.012222088, 0.012222088, 
       0.072221428, 0.052221648, 0.087776810,0.014444285, 0.033332966, 0.012222088, 
       0.032221869, 0.059999339, 0.011110989, 0.011110989,0.042221759, 0.029999670, 
       0.018888680, 0.098887801, 0.016666483, 0.031110767, 0.061110441,0.022221979, 
       0.073332526, 0.012222088, 0.016666483, 0.012222088, 0.122220881, 0.134442955, 
       0.094443403, 0.128887475, 0.045555055, 0.152220547, 0.071110331, 0.018888680,
       0.022221979, 0.029999670, 0.035555165, 0.014444285, 0.049999449, 0.074443623, 
       0.068888135, 0.062221535, 0.032221869, 0.095554501, 0.143331751, 0.121109776,
       0.065554835, 0.074443623, 0.043332856, 0.017777583, 0.016666483, 0.036666263, 
       0.152220547, 0.032221869, 0.009999890, 0.009999890, 0.021110879, 0.025555275,
       0.099998899, 0.015555384, 0.086665712, 0.008888791, 0.062221535, 0.044443958, 
       0.081110224, 0.015555384, 0.089999005, 0.082221314, 0.056666043, 0.013333187,
       0.048888352, 0.075554721, 0.025555275, 0.056666043, 0.146665052, 0.118887581, 
       0.125554174, 0.024444176, 0.124443069, 0.012222088, 0.126665279, 0.048888352,
       0.046666153, 0.141109571, 0.015555384, 0.114443190)

plot(y, type="l", lty = 3, main="Savitzky-Golay with l = 51, 25, 10")
  lines(sg.smooth(y),col="red", lwd=2)
  lines(sg.smooth(y, l = 25),col="blue", lwd=2)
  lines(sg.smooth(y, l = 10),col="green", lwd=2)
  
#### function applied to a multi-band raster 
library(terra)
( r <- spatialEco::random.raster(n.layers=20) )

# raster stack example
( r.sg <- app(r, sg.smooth) )  
 

jeffreyevans/spatialEco documentation built on April 4, 2024, 10:53 a.m.