oce runlm function
Feb 11, 2014
The weekold ``runderiv()`` function has been replaced with a more useful ``runlm()`` function. This post shows how to use it.
Introduction
As was expected, the runderiv()
function has been both useful and deficient. Useful because it offers a good replacement for smooth.spline()
calculations of derivatives for things like N^2. And deficient because it only calculated derivatives, not values!
Both an extension and a renaming were called for. The result is runlm()
.
Tests
Below are the examples from its manpage, with the results.
Case 1
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library(oce)
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x < 1:100
y < 1 + x/100 + sin(x/5)
yn < y + rnorm(100, sd=0.1)
L < 4
calc < runlm(x, y, L=L, deriv=0)
plot(x, y, type='l', lwd=7, col='gray')
points(x, yn, pch=20, col='blue')
lines(x, calc, lwd=2, col='red')
Case 2
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data(ctd)
plot(ctd, which="N2")
rho < swRho(ctd)
z < swZ(ctd)
zz < seq(min(z), max(z), 0.1)
N2 < 9.8 / mean(rho) * runlm(z, rho, zz, deriv=1)
lines(N2, zz, col='red')
legend("bottomright", lwd=2, bg="white",
col=c("black", "red"),
legend=c("swN2()", "using runlm()"))
Comments

The fit in Case 1 is almost spookily good.

The N^2 results suggest including this as a method for
swN2()
, perhaps the default method, but thatâ€™s for another day.
Resources
 Source code: 20140411runlm.R