| 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")