Non-exported function, newknots are used in the cpr and
cnr calls. Used to create a new control polygon or control net
from with different internal knots.
Value
Expected use is within the cpr and cnr calls. The
return object a formula to define a control polygon/net
with different knots than then ones found within form.
Details
Think of this function as an analogue to the stats{update}
calls. Where stats{update} will modify a call, the
newknots will update just the iknots argument of a
bsplines or btensor call within the formula argument of
a cp or cn call.
See also
update_bsplines for a more generic tool for the end
user.
Examples
cp0 <- cp(log(pdg) ~ bsplines(day, iknots = c(-.25, 0, 0.25), bknots = c(-1, 1)), data = spdg)
new_knots <- c(-0.85, 0, 0.25, 0.3)
f <- cpr:::newknots(cp0$call$formula, nk = new_knots)
f
#> log(pdg) ~ bsplines(day, iknots = c(-0.85, 0, 0.25, 0.3), bknots = c(-1,
#> 1))
#> NULL
cp(f, data = spdg)
#> xi_star theta
#> 1 -1.0000000 -0.007699847
#> 2 -0.9500000 -0.439608186
#> 3 -0.6166667 -1.086005675
#> 4 -0.2000000 -1.657347591
#> 5 0.1833333 0.570416069
#> 6 0.5166667 1.960042179
#> 7 0.7666667 1.477610529
#> 8 1.0000000 0.088837397