
swN2(pressure, sigmaTheta=NULL, derivs, ...)
sigmaTheta
must
be provided) or an object of class ctd
object (in which case
sigmaTheta
is inferred from the object.smooth.spline
. See Details.ctd
object, then
sigmaTheta
is inferred from it. The result is calculated from the derivative of a smoothing cubic
spline fitted to the density profile using smooth.spline
.
Optional arguments in ...are passed to this routine, providing the
user with a good degree of control over the smoothing technique. A
common method is to set df
, the degrees of freedom for the
spline fit. (Note that if df
is not provided as an argument,
swN2
will set it to min(length(p)/5, 10)
to provide a
result similar to what one might calculate by smoothing the density
profile manually.)
library(oce)
data(ctd)
# Illustrate effect of changing df
p <- pressure(ctd)
plot(swN2(ctd), p, ylim=rev(range(p)), xlab="N2",ylab="p", type='l')
lines(swN2(ctd, df=3), p, col="blue")
grid()
Run the code above in your browser using DataLab