bKriging: Regional Mean Estimation by Block Kriging

In lspatial/sptemUS: Constrained Spatiotemporal Mixed-Effect Models for Exposure Estimation of Air Pollutants

Description

Block Kriging can use the measured or prediceted values to estimate the regional mean with minimum variance.

Usage

bKriging(samples, rtargets,tarStr,paras,model)

Arguments

samples	the sample data used to estimate the regional mean, must include the x and y coordinates. Format:DataFrame.
rtargets	the points within the target region used to represent the region to be predicted for the regional means. The points determines the density, shape and size of the region. Format:dataframe
tarStr	The target variable name (field name)
paras	variogram parameters: format: vector, (range,sill,nugget)
model	variogram model: default: "exponential"

Value

vector format: (kriged mean, kriged standard deviation, regular average, regular standard deviation)

Author(s)

Lianfa Li [e-mail]

Examples

#Test for simulated data

dataDt=data.frame(x=sample(c(1:3000),100),y=sample(c(1:2500),100))
dataDt$z=(2*dataDt$x+5*dataDt$y)
dataDtSp=dataDt
sp::coordinates(dataDtSp) <- ~x+y
cl=colorGrinf(dataDt$z)
raster::plot(dataDtSp,col=cl$cols[cl$index])
tarDt=data.frame()
for(i in c(1:10)){
  for(j in c(1:10)){
    index=(i-1)*10+j
    tarDt[index,"x"]=i*10
    tarDt[index,"y"]=j*10
  }
}

varg=automap::autofitVariogram(z~1,input_data =dataDtSp,model="Exp")
paras=c(varg$var_model[2,3],varg$var_model[2,2],varg$var_model[1,2])
krigeMean=bKriging(dataDt, tarDt,"z",paras,model="Exp")
krigeMean


#Test using PM2.5 data of the 2014 PM2.5 of Shandong province

data("spointspre")
spointspresub=spointspre[!is.na(spointspre$pre_m),]
spointspresub$log_pre=log(spointspresub$pre_m)
sz=as.integer(nrow(spointspresub)/1)
index=sample(c(1:sz),size=as.integer(sz/2))
samples=spointspresub[index,]
rtargets=(spointspresub[c(1:sz),])[-index,]
paras=c(50000,0.0278,0.2)
samples@data$x=sp::coordinates(samples)[1]
samples@data$y=sp::coordinates(samples)[2]
rtargets@data$x=sp::coordinates(rtargets)[1]
rtargets@data$y=sp::coordinates(rtargets)[2]
sampledata=samples@data
rtargetsdata=rtargets@data
krigeMean=bKriging(sampledata, rtargetsdata,"log_pre",paras,model="Exp")
exp(krigeMean)

lspatial/sptemUS documentation built on May 29, 2019, 3:42 a.m.