influence_of_iknots {cpr}

Determine the influence of the internal knots of a control polygon

Description

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