object of STFDF-class containing dependent variable (observations) in space and time.
zcol
variable column name or number showing position of dependent variable in temp@data
newdata
dynamic and static covariates as STFDF-class object; spatial and temporal overlay with temp object must be possible
pred.id
identifier of new variable
zero.tol
distance values less than or equal to this threshold value locations are considered as duplicates, see rm.dupl, duplicates are removed to avoid singular covariance matrices in kriging.
dynamic.cov
vector of variable column names or numbers showing position of dynamic covariates in newdat@data; dynamic covariates are spatio-temporal explanatory variables, changing in space and time domain
static.cov
vector of variable column names or numbers showing position of static covariates in newdata@data@sp; static covariates are spatial explanatory variables changing just in space; static in time dimension
reg.coef
linear regression coefficients; order is assumed as intercept, dynamic.cov, static.cov. Coefficients can be specified by user; depending on type, number and order of dynamic and static covariates. At the moment the function contains regression coefficient for mean, minimum and maximum temperature calculated globally for GSOD and ECA&D data set on geometrical temperature trend, MODIS LST-8 day, elevation and TWI, see regdata. Coefficients for mean temperature are defined by default.
vgm.model
spatio-temporal variogram of regression residuals, see vgmST. At the moment the function contains spatio-temporal variogram model on residuals for mean, minimum and maximum temperature calculated globally for GSOD and ECA&D data set. Regression residuals on geometrical temperature trend, MODIS LST-8 day, elevation and TWI, see regdata. Ranges are in km. Spatio-temporal variogram for mean temperatures is defined by default. User can specified own variogram model as vgmST object.
tiling
for simplified local kriging. Area is divided in tiles and kriging calculation is done for each tile separately, number of observation used per tile is defined with sp.nmax and time.nmax. Default is TRUE. If FALSE just temporal local kriging will be applied defined with time.nmax, sp.nmax will be ignored.
ntiles
number of tiles. Default is 64. Each tile at minimum should contain less observations than sp.nmax, ideally each tile should contain observations falling in neighboring tiles.
parallel.processing
if TRUE parallel processing is performed via sfLapply
cpus
number of processing units
sp.nmax
number of nearest spatial observations that should be used for a kriging prediction for each tile
time.nmax
number of nearest time observations that should be used for a kriging prediction
fast
if TRUE tiling, tiling is done twice to avoid edge effect
computeVar
if TRUE, just variance is computed
do.cv
if TRUE, cross validation leave-one-station-out is performed
only.cv
if TRUE, only cross validation leave-one-station-out is performed without prediction
out.remove
if TRUE, potential outliers are removed. Removing procedure is iterative, all location with residual higher than defined threshold (treshold.res) are selected. Only location with highest cross validation residual is removed, than cross validation is done again, the procedure removing one by one location run until all locations have residuals under defined threshold.
threshold.res
critical threshold for removing potential outliers
progress
if FALSE remove progress bar
Value
An list object containing:
pred
an object of STFDF-class with column contains prediction or variance
cv
cross validation information for points used in prediction, as object of STFDF-class
out
potential outliers, returned as vector of row names of x$cv@sp, only returned if out.remove=FALSE
remst
removed locations as an object of Spatial-class, if out.remove=TRUE
remobs
removed locations with observations as an object of STFDF-class, if out.remove=TRUE
Kilibarda, M., T. Hengl, G. B. M. Heuvelink, B. Graeler, E. Pebesma, M. Percec Tadic, and B. Bajat (2014), Spatio-temporal interpolation of daily temperatures for global land areas at 1 km resolution, J. Geophys. Res. Atmos., 119, 2294-2313, doi:10.1002/2013JD020803.
See Also
regdatameteo2STFDFtgeom2STFDF
Examples
# prepare data
# load observation - data.frame of mean temperatures
data(dtempc)
# str(dtempc)
data(stations)
library(sp)
library(spacetime)
library(gstat)
# str(stations)
## lonmin,lonmax,lonmax, lonmin latmin, latnmin,latmax,latmax
serbia= point.in.polygon(stations$lon, stations$lat, c(18,22.5,22.5,18), c(40,40,46,46))
st= stations[ serbia!=0, ]
# create STFDF
temp <- meteo2STFDF(dtempc,st)
rm(dtempc)
# str(temp)
# Adding CRS
temp@sp@proj4string <- CRS('+proj=longlat +datum=WGS84')
# load covariates for mean temperatures
data(regdata)
# str(regdata)
regdata@sp@proj4string <- CRS('+proj=longlat +datum=WGS84')
# Calculate prediction of mean temperatures for "2011-07-05"
# global model is used for regression and variogram
# load precalculated variograms
data(tvgms)
data(tregcoef)
res= pred.strk(temp,zcol=1, newdata= regdata[,1,drop=FALSE],
reg.coef=tregcoef[[1]] ,vgm.model=tvgms[[1]], progress=FALSE )
## plot prediction
# stplot(res$pred, col.regions=bpy.colors())
# t1= temp[regdata@sp,]
# # create fake observations
# t1@data$tempc[seq(1,120,by=8)] =35
#
#
# res= pred.strk(t1,zcol=1, newdata= regdata[,1:2],
# reg.coef=tregcoef[[1]], vgm.model=tvgms[[1]] ,
# threshold.res=5, do.cv=T, out.remove = T)
# # plot cross validation residuals
# stplot(res$cv[,,'resid.cv'] , col.regions=bpy.colors())
#
# # plot locations of removed stations
# spplot(res$remst, zcol='station_name' , col.regions=bpy.colors())
# #plot removed stations as time-series
# row.names(res$remobs@sp) = res$remst$station_name
# res$remobs[,1:2,c('tempc','pred.cv')]
# stplot(res$remobs[,1:2,c('tempc','pred.cv')], mode='tp')
## Calculate prediction of mean temperature for "2011-07-05" "2011-07-06"
## only MODIS is used as covariate
# modisVGM =vgmST("sumMetric",space=vgm( 18.27, "Sph", 6000, 3.22),
# time =vgm(0, "Sph", 0.1, 0),
# joint=vgm(8.34, "Sph", 2349, 1.80),
# stAni=583)
# attr(modisVGM,"temporal unit") = "days"
# rkmod <- pred.strk(temp,zcol=1, newdata= STFDF(regdata@sp,
# time=as.POSIXct("2011-07-05"), endTime=as.POSIXct("2011-07-06"),
# data=regdata[,1]@data) , threshold.res=10,
# dynamic.cov='modis', static.cov=NULL,
# reg.coef= c(-0.23,0.7303284),
# vgm.model= modisVGM )
## coefficients and variogram is calculated globally for GSOD and ECA&D obs. for 2011 year
# stplot(rkmod$pred, col.regions=bpy.colors())
## parallel processing
# library(snowfall)
# rkmod <- pred.strk(temp,zcol=1,
# newdata= STFDF(regdata@sp,
# time=as.POSIXct("2011-07-05"), endTime=as.POSIXct("2011-07-06"),
# data=regdata[,1]@data) ,
# threshold.res=10,
# dynamic.cov='modis', static.cov=NULL,
# reg.coef= c(-0.23,0.7303284),
# vgm.model= modisVGM, parallel.processing=TRUE)