cpr (version 0.4.1)

sign_changes: Sign Changes

Description

Count the number of times the first, or second, derivative of a spline changes sign.

Usage

sign_changes(
  object,
  lower = min(object$bknots),
  upper = max(object$bknots),
  n = 1000,
  derivative = 1L,
  ...
)

Value

the number of times the sign of the first or second derivative changes within the specified interval.

Arguments

object

a cpr_cp object

lower

the lower limit of the integral

upper

the upper limit of the integral

n

number of values to assess the derivative between lower and upper.

derivative

integer value denoted first or second derivative

...

pass through

See Also

wiggle

Examples

xvec <- seq(0, 6, length = 500)

# Define the basis matrix
bmat1 <- bsplines(x = xvec, iknots = c(1, 1.5, 2.3, 4, 4.5))
bmat2 <- bsplines(x = xvec)

# Define the control vertices ordinates
theta1 <- c(1, 0, 3.5, 4.2, 3.7, -0.5, -0.7, 2, 1.5)
theta2 <- c(1, 3.4, -2, 1.7)

# build the two control polygons
cp1 <- cp(bmat1, theta1)
cp2 <- cp(bmat2, theta2)
plot(cp1, cp2, show_cp = FALSE, show_spline = TRUE)

sign_changes(cp1)
sign_changes(cp2)