| krige {gstat} | R Documentation |
Function for simple, ordinary or universal kriging (sometimes called external drift kriging), kriging in a local neighbourhood, point kriging or kriging of block mean values (rectangular or irregular blocks), and conditional (Gaussian or indicator) simulation equivalents for all kriging varieties, and function for inverse distance weighted interpolation. For multivariable prediction, see gstat and predict.gstat
krige(formula, locations, ...)
krige.locations(formula, locations, data, newdata, model, ..., beta, nmax
= Inf, nmin = 0, maxdist = Inf, block, nsim = 0, indicators = FALSE,
na.action = na.pass, debug.level = 1)
krige.spatial(formula, locations, newdata, model, ..., beta, nmax
= Inf, nmin = 0, maxdist = Inf, block, nsim = 0, indicators = FALSE,
na.action = na.pass, debug.level = 1)
krige0(formula, data, newdata, model, beta, y)
idw(formula, locations, ...)
idw.locations(formula, locations, data, newdata, nmax = Inf,
nmin = 0, maxdist = Inf, block, na.action = na.pass, idp = 2.0,
debug.level = 1)
idw.spatial(formula, locations, newdata, nmax = Inf, nmin = 0,
maxdist = Inf, block = numeric(0), na.action = na.pass, idp = 2.0,
debug.level = 1)
idw0(formula, data, newdata, y)
formula |
formula that defines the dependent variable as a linear
model of independent variables; suppose the dependent variable has name
z, for ordinary and simple kriging use the formula z~1;
for simple kriging also define beta (see below); for universal
kriging, suppose z is linearly dependent on x and y,
use the formula z~x+y |
locations |
object of class Spatial, or (deprecated)
formula defines the spatial data locations (coordinates) such as ~x+y |
data |
data frame: should contain the dependent variable, independent variables, and coordinates, should be missing if locations contains data. |
newdata |
data frame or Spatial object with prediction/simulation
locations; should
contain attribute columns with the independent variables (if present) and
(if locations is a formula) the coordinates with names as defined in locations |
model |
variogram model of dependent variable (or its residuals),
defined by a call to vgm or fit.variogram; for krige0
also a user-supplied covariance function is allowed (see example below) |
beta |
for simple kriging (and simulation based on simple kriging): vector with the trend coefficients (including intercept); if no independent variables are defined the model only contains an intercept and beta should be the simple kriging mean |
nmax |
for local kriging: the number of nearest observations that should be used for a kriging prediction or simulation, where nearest is defined in terms of the space of the spatial locations. By default, all observations are used |
nmin |
for local kriging: if the number of nearest observations
within distance maxdist is less than nmin, a missing
value will be generated; see maxdist |
maxdist |
for local kriging: only observations within a distance
of maxdist from the prediction location are used for prediction
or simulation; if combined with nmax, both criteria apply |
block |
block size; a vector with 1, 2 or 3 values containing the size of a rectangular in x-, y- and z-dimension respectively (0 if not set), or a data frame with 1, 2 or 3 columns, containing the points that discretize the block in the x-, y- and z-dimension to define irregular blocks relative to (0,0) or (0,0,0)—see also the details section of predict.gstat. By default, predictions or simulations refer to the support of the data values. |
nsim |
integer; if set to a non-zero value, conditional simulation
is used instead of kriging interpolation. For this, sequential Gaussian
or indicator simulation is used (depending on the value of
indicators), following a single random path through the data. |
indicators |
logical, only relevant if nsim is non-zero; if
TRUE, use indicator simulation; else use Gaussian simulation |
na.action |
function determining what should be done with missing values in 'newdata'. The default is to predict 'NA'. Missing values in coordinates and predictors are both dealt with. |
debug.level |
debug level, passed to predict.gstat; use -1 to see progress in percentage, and 0 to suppress all printed information |
... |
other arguments that will be passed to gstat |
idp |
numeric; specify the inverse distance weighting power |
y |
matrix; to krige multiple fields in a single step, pass data
as columns of matrix y. This will ignore the value of the
response in formula. |
Function krige is a simple wrapper method around gstat
and predict.gstat for univariate kriging prediction and conditional
simulation methods available in gstat. For multivariate prediction or
simulation, or for other interpolation methods provided by gstat (such as
inverse distance weighted interpolation or trend surface interpolation)
use the functions gstat and predict.gstat directly.
Function idw performs just as krige without a model being
passed, but allows direct specification of the inverse distance weighting
power. Don't use with predictors in the formula.
For further details, see predict.gstat.
if locations is not a formula, object of the same class as
newdata (deriving from Spatial); else a data frame
containing the coordinates of newdata. Attributes columns
contain prediction and prediction variance (in case of kriging) or the
abs(nsim) columns of the conditional Gaussian or indicator
simulations
krige0 and idw0 are alternative functions that have reduced
functionality and larger memory requirements; they return numeric vectors
with predicted values only.
data refer to spatial coordinates
Daniel G. Krige is a South African scientist who was a mining engineer
when he first used generalised least squares prediction with spatial
covariances in the 50's. George Matheron coined the term kriging
in the 60's for the action of doing this, although very similar approaches
had been taken in the field of meteorology. Beside being Krige's name,
I consider "krige" to be to "kriging" what "predict" is to "prediction".
Edzer J. Pebesma
N.A.C. Cressie, 1993, Statistics for Spatial Data, Wiley.
Pebesma, E.J., 2004. Multivariable geostatistics in S: the gstat package. Computers & Geosciences, 30: 683-691.
data(meuse)
coordinates(meuse) = ~x+y
data(meuse.grid)
gridded(meuse.grid) = ~x+y
m <- vgm(.59, "Sph", 874, .04)
# ordinary kriging:
x <- krige(log(zinc)~1, meuse, meuse.grid, model = m)
spplot(x["var1.pred"], main = "ordinary kriging predictions")
spplot(x["var1.var"], main = "ordinary kriging variance")
# simple kriging:
x <- krige(log(zinc)~1, meuse, meuse.grid, model = m, beta = 5.9)
# residual variogram:
m <- vgm(.4, "Sph", 954, .06)
# universal block kriging:
x <- krige(log(zinc)~x+y, meuse, meuse.grid, model = m, block = c(40,40))
spplot(x["var1.pred"], main = "universal kriging predictions")
# krige0, using user-defined covariance function and multiple responses in y:
# exponential variogram with range 500, defined as covariance function:
v = function(x,y) { exp(-spDists(coordinates(x),coordinates(y))/500) }
y = cbind(meuse$zinc,meuse$copper,meuse$lead,meuse$cadmium)
x <- krige0(zinc~1, meuse, meuse.grid, v, y = y)
meuse.grid$zinc = x[,1]
spplot(meuse.grid["zinc"], main = "zinc")
meuse.grid$copper = x[,2]
spplot(meuse.grid["copper"], main = "copper")
# etc.