Determine the influence of the internal knots of a control polygon

Usage

influence_of_iknots(x, verbose = FALSE, ...)

# S3 method for class 'cpr_cn'
influence_of_iknots(
  x,
  verbose = FALSE,
  margin = seq_along(x$bspline_list),
  n_polycoef = 20L,
  ...
)

Arguments

x: cpr_cp or cpr_cn object
verbose: print status messages
...: pass through
margin: which margin(s) to consider the influence of iknots
n_polycoef: number of polynomial coefficients to use when assessing the influence of a iknot

Value

a cpr_influence_of_iknots object. A list of six elements:

original_cp
coarsened_cps
restored_cps
d
influence
chisq

Examples

x <- seq(0 + 1/5000, 6 - 1/5000, length.out = 5000)
bmat <- bsplines(x, iknots = c(1, 1.5, 2.3, 4, 4.5), bknots = c(0, 6))
theta <- matrix(c(1, 0, 3.5, 4.2, 3.7, -0.5, -0.7, 2, 1.5), ncol = 1)
cp0 <- cp(bmat, theta)

icp0 <- influence_of_iknots(cp0)

plot(cp0, icp0$coarsened_cps[[1]], icp0$restored_cps[[1]], color = TRUE, show_spline = TRUE)

plot(cp0, icp0$restored_cps[[1]], color = TRUE, show_spline = TRUE)


plot(cp0, icp0$coarsened_cps[[2]], icp0$restored_cps[[2]], color = TRUE, show_spline = TRUE)

plot(cp0, icp0$restored_cps[[2]], color = TRUE, show_spline = TRUE)


plot(cp0, icp0$coarsened_cps[[3]], icp0$restored_cps[[3]], color = TRUE, show_spline = TRUE)

plot(cp0, icp0$restored_cps[[3]], color = TRUE, show_spline = TRUE)


plot(cp0, icp0$coarsened_cps[[4]], icp0$restored_cps[[4]], color = TRUE, show_spline = TRUE)

plot(cp0, icp0$restored_cps[[4]], color = TRUE, show_spline = TRUE)


plot(cp0, icp0$coarsened_cps[[5]], icp0$restored_cps[[5]], color = TRUE, show_spline = TRUE)

plot(cp0, icp0$restored_cps[[5]], color = TRUE, show_spline = TRUE)


# When the cp was defined by regression
df <- data.frame(x = x, y = as.numeric(bmat %*% theta) + rnorm(5000, sd = 0.2))
cp1 <- cp(y ~ bsplines(x, iknots = c(1, 1.5, 2.3, 3, 4, 4.5), bknots = c(0, 6)), data = df)
icp1 <- influence_of_iknots(cp1)
icp1
#>         xi_5         xi_6         xi_7         xi_8         xi_9        xi_10 
#> 1.541257e+00 2.123213e-01 6.530531e-02 8.792049e-05 2.306098e-02 2.712189e-01