dbsp {bspline} | R Documentation |
Derivative of B-spline
dbsp(f, nderiv = 1L, same_xk = FALSE)
f |
Function, B-spline such as returned by |
nderiv |
Integer scalar >= 0, order of derivative to calculate (1 by default) |
same_xk |
Logical scalar, if TRUE, indicates to calculate derivative on the same knot grid as original function. In this case, coefficient number will be incremented by 2. Otherwise, extreme knots are removed on each side of the grid and coefficient number is maintained (FALSE by default). |
Function calculating requested derivative
x=seq(0., 1., length.out=11L)
y=sin(2*pi*x)
f=smbsp(x, y, nki=2L)
d_f=dbsp(f)
xf=seq(0., 1., length.out=101) # fine grid for plotting
plot(xf, d_f(xf)) # derivative estimated by B-splines
lines(xf, 2.*pi*cos(2*pi*xf), col="blue") # true derivative
xk=bsppar(d_f)$xk
points(xk, d_f(xk), pch="x", col="red") # knot positions