Usage
pointkriging(lat, lon, z, xgr, vagram, maxnumber = 16, scale = "km", option = 1, maxdist = 0, rat = 3, nb = 8, set = 0, areas = 0, varcalc = F, sill = 0, minnumber = 2, suboption = 1, outside = T, degree = 0, lognormal = F, zeroset = F)
Arguments
lat
Latitude of datapoints.
lon
Longitude of datapoints.
xgr
Description of the grid. Can be output from program grid or just
a list with components \$lat and \$lon.
vagram
Components of the variogram, a list with a least 3 components,
\$sill, \$nugget & \$rang1.
maxnumber
Number of neighbourhood points used , default is 16. In
some cases 16 points are not found.
scale
Scale "km" or "miles", default is "miles".
option
Option used for selecting neighbourhood points. Allowed
values 1,2,3 and 4. Default value is one. For further information see
below.
maxdist
If option = 4 all points within maxdist are used. If option
= 4 the default value of maxdist is the range of the variogram. maxdist has
also meaning when option = 1,2 or 3. In those cases points further away
from any datapoint than maxdist are set to zero, mean z or NA.
rat
The number of points in the first step of the search is
rat*maxnumber.
nb
Parameter describing the extent of the area where neighbourhood
points are searched in the first round. Default value is 8 which means that
and area of 16x16 gridpoints is searched.
set
Points outside region or further away than maxdist from any
datapoint are set to either zero (set=0) or mean(z) set=1 or NA set =-1.
areas
A list defining a number of areas. NA is between areas.
Points in different areas are treated as independed. Two neighbourhood
fjords could be defined as different areas so the program does not
interpolate between them.
varcalc
If varcalc is true the estimation variance at each datapoint
is calculated. Default value is F.
sill
Sill in variance calculations. Default value is the sill of the
variogram.
minnumber
If number of neighbourhood points found is less than or
equal to minnumber the point is considered outside the areas covered by the
datapoints and set to NA,0 or mean(z)
suboption
If option = 4 and more than maxnumber points are found in
the area the program switches to option 1, 2 or 3 in the point search.
Default value is 1.
outside
If outside is T points further away from the area than nb*dx
are excluded. dx is the grid interval. Too many points outside of the area
can problems in the search because the grid is used to divide the area in
squares and everything left and below the first gridpoint is for example one
square.
degree
Degree of drift polynomial for universal kriging. 0, 1 or 2.
Default 0.
lognormal
To be described.