smoothVariogram {BiSeq} | R Documentation |
Nonparametric smoothing with kernel regression estimators and adaptable bandwidth for variogram smoothing.
smoothVariogram(variogram, sill, bandwidth)
variogram |
A |
sill |
A |
bandwidth |
A numeric vector of same length as the variogram (number of
rows). Default: |
It is necessary to smooth the variogram. Especially for greater
h
the variogram tends to oscillate strongly. This is the reason
why the default bandwidth increases with increasing
h
. Nevertheless, the smoothed variogram may further increase or
decrease after a horizontal part (sill). This is mostly due to the small number
of observations for high distances. To wipe out this bias it is useful to
set the smoothed variogram to a fixed value above a certain h
, usually the mean value of the
horizontal part. If a smoothed value v.sm is greater than
sill
for distance h_{range}, this v.sm and all other
smoothed values with h > h_{range} are set to sill
. Internally, the function lokerns
from package lokerns
is used for smoothing.
The variogram matrix (or a list with the variogram matrix) with an additional column of the smoothed
v
values.
Katja Hebestreit
makeVariogram
, lokerns
data(vario) # Find out the sill (this is more obvious for larger data sets): plot(vario$variogram$v) vario.sm <- smoothVariogram(vario, sill = 0.9) plot(vario$variogram$v) lines(vario.sm$variogram[,c("h", "v.sm")], col = "red")