wFUN: Weight updating functions

In kongdd/whittaker: Whittaker smoother

Description

• wSELF weigth are not changed and return the original.

• wTSM weight updating method in TIMESAT.

• wBisquare Bisquare weight update method. wBisquare has been modified to emphasis on upper envelope.

• wChen Chen et al., (2004) weight updating method.

• wBeck Beck et al., (2006) weigth updating method. wBeck need sos and eos input. The function parameter is different from others. It is still not finished.

Usage

wSELF(y, yfit, w, ...)

wBisquare(y, yfit, w, ..., wmin = 0.2)

wChen(y, yfit, w, ..., wmin = 0.2)

wKong(y, yfit, w, ..., wmin = 0.2)

Arguments

y	Numeric vector, vegetation index time-series
yfit	Numeric vector curve fitting values.
w	(optional) Numeric vector, weights of y. If not specified, weights of all NA values will be wmin, the others will be 1.0.
...	other parameters are ignored.
iter	iteration of curve fitting.
wfact	weight adaptation factor (0-1), equal to the reciprocal of 'Adaptation strength' in TIMESAT.

Value

wnew Numeric Vector, adjusted weights.

References

1. Per J"onsson, P., Eklundh, L., 2004. TIMESAT - A program for analyzing time-series of satellite sensor data. Comput. Geosci. 30, 833-845. https://doi.org/10.1016/j.cageo.2004.05.006.
   

2. https://au.mathworks.com/help/curvefit/smoothing-data.html#bq_6ys3-3
   

3. Garcia, D., 2010. Robust smoothing of gridded data in one and higher dimensions with missing values. Computational statistics & data analysis, 54(4), pp.1167-1178.
   

4. 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.
   

5. Beck, P.S.A., Atzberger, C., Hogda, K.A., Johansen, B., Skidmore, A.K., 2006. Improved monitoring of vegetation dynamics at very high latitudes: A new method using MODIS NDVI. Remote Sens. Environ. https://doi.org/10.1016/j.rse.2005.10.021
   

6. https://github.com/kongdd/phenopix/blob/master/R/FitDoubleLogBeck.R

kongdd/whittaker documentation built on June 4, 2019, 7:49 a.m.