Last data update: 2014.03.03

R: Median polish trend
removetrendMPstR Documentation

Median polish trend

Description

Direct method to remove trend of spatio - temporal data througth median polish.

Usage

removetrendMPst(MPST,eps=0.01, maxiter=10L)

Arguments

MPST

object of class ConstructMPst

eps

real number greater than 0, default 0.01. A tolerance for convergence of median polish.

maxiter

the maximum number of iterations. Default 10.

Details

Robust method introduced for Cressie(1993) and enhanced by Berke(2001) to remove trend of a space - time process with data ≤ft{y(mathbf{s}_{abc},t), a=1,...,U; b=1,...,V; c=1,...,W, t=1,...,n ight}

Y(mathbf{s}_{abc},t)= μ_{y}(mathbf{s}_{abc},t) + δ _{abct}

where

μ _{y}(mathbf{s}_{abc},t)= μ +α _{a} + β _{b} + ξ _{c} + τ _{t}

and δ _{abct} is a fluctuation arising from natural variability and from the measurement process. Additionally, μ is an overall mean, α_{a} is the a-th row effect, β_{b} is the effect b-th column effect, ξ_{c} is the c-th layer effect, τ _{t} is the t-th time effect.

Value

data.frame with the following fields:

ET

indicate the time of a observation

x

spatial coordinates x

y

spatial coordinates y

z

spatial coordinates z

Trend

trend calculated through median polish space - time

Value

observed values

Residual

Residual = Value-Trend

References

Berke, O. (2001). Modified median polish kriging and its application to the wolfcamp - aquifer data. Environmetrics, 12(8):731-748.[link]

Cressie, N. (1993). Statistics for spatial data. Wiley series in probability and statistics.[link]

Examples

## Not run:
data(Metadb)
x<-matrix(0,1,37)
for(i in 1:37){
 x[,i] <- 2007 + (seq(0, 36)/12)[i]
}
x<-as.Date (as.yearmon(x), frac = 1)
time = as.POSIXct(x, tz = "GMT")

MPST<-ConstructMPst(Metadb[,-c(1:4)],time,pts=Metadb[,2:4],Delta=c(7,6,5))
residuals<-removetrendMPst(MPST,eps=0.01, maxiter=2)
## End(Not run)

Results


R version 3.3.1 (2016-06-21) -- "Bug in Your Hair"
Copyright (C) 2016 The R Foundation for Statistical Computing
Platform: x86_64-pc-linux-gnu (64-bit)

R is free software and comes with ABSOLUTELY NO WARRANTY.
You are welcome to redistribute it under certain conditions.
Type 'license()' or 'licence()' for distribution details.

R is a collaborative project with many contributors.
Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.

Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for an HTML browser interface to help.
Type 'q()' to quit R.

> library(STMedianPolish)
Loading required package: maptools
Loading required package: sp
Checking rgeos availability: TRUE
Loading required package: reshape2
Loading required package: spacetime
Loading required package: zoo

Attaching package: 'zoo'

The following objects are masked from 'package:base':

    as.Date, as.Date.numeric

> png(filename="/home/ddbj/snapshot/RGM3/R_CC/result/STMedianPolish/removetrendMPst.Rd_%03d_medium.png", width=480, height=480)
> ### Name: removetrendMPst
> ### Title: Median polish trend
> ### Aliases: removetrendMPst
> 
> ### ** Examples
> 
> ## Not run:
> data(Metadb)
> x<-matrix(0,1,37)
> for(i in 1:37){
+  x[,i] <- 2007 + (seq(0, 36)/12)[i]
+ }
> x<-as.Date (as.yearmon(x), frac = 1)
> time = as.POSIXct(x, tz = "GMT")
> 
> MPST<-ConstructMPst(Metadb[,-c(1:4)],time,pts=Metadb[,2:4],Delta=c(7,6,5))
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> residuals<-removetrendMPst(MPST,eps=0.01, maxiter=2)
   |                                                                               |                                                                      |   0%   |                                                                               |============                                                          |  17%   |                                                                               |=======================                                               |  33%   |                                                                               |===================================                                   |  50%   |                                                                               |===============================================                       |  67%   |                                                                               |==========================================================            |  83%   |                                                                               |======================================================================| 100%
> ## End(Not run)
> 
> 
> 
> 
> 
> dev.off()
null device 
          1 
>