R: Collapse repeated spatial locations into unique locations

Krig.replicates {fields} | R Documentation

## Collapse repeated spatial locations into unique locations

### Description

In case that several observations are available for a single spatial location find the group means and replicate variability

### Usage

    Krig.replicates(out, x, y, Z, weights=rep( 1, length(y)), verbose = FALSE)

### Arguments

`out` | A list with components `x`, `y`, `weights`, and possibily `Z`.
`x` | Spatial locations.
`y` | Spatial observations
`Z` | Spatial covariates.
`weights` | Weights proportional to reciprocal varainces of observations.
`verbose` | If TRUE print out details for debugging.

### Details

This function figures out which locations are the same and within the function fast.1way use `tapply` to find replicate group means and standard deviations. NOTE: it is assumed the Z covariates are unique at the locations. Currently these functions can not handle a model with common spatial locations but different values for the Z covariates.

### Value

A list with components:

`yM` | Data at unique locations and where more than one observation is available this is the mean of the replicates.
`xM` | Unique spatial locations.
`weightsM` | Weights matching the unique lcoations proportional to reciprocal variances This is found as a combination of the original weights at each location.
`ZM` | Values of the covariates at the unique lcoations.
`uniquerows` | Index for unique rows of `x`.
`shat.rep, shat.pure.error` | Standard deviation of pure error estimate based on replicate groups (and adjusting for possibly different weights.)
`rep.info` | Integer tags indicating replicate groups.

### Author(s)

Douglas Nychka

### Examples

    #create  some spatial replicates
     set.seed( 123)
     x0<- matrix( runif(10*2), 10,2)
     x<-  x0[ c(rep(1,3), 2:8, rep( 9,5),10) , ]
     y<-  rnorm( 16)

     out<- Krig.replicates( x=x, y=y)
    # compare
    # out$yM[1] ;  mean( y[1:3])
    # out$yM[9] ; mean( y[11:15])
    # mean( y[ out$rep.info==9])

[Package fields version 9.6.1 Index]