pchip {signal} | R Documentation |
Piecewise cubic hermite interpolation.
pchip(x, y, xi = NULL)
x,y |
vectors giving the coordinates of the points to be
interpolated. x must be strictly monotonic
(either increasing or decreasing). |
xi |
points at which to interpolate. |
In contrast to spline
, pchip
preserves the monotonicity of
x
and y
.
Normally, the interpolated signal, an array of length(xi)
.
if xi == NULL
, a list of class pp
, a piecewise
polynomial representation with the following elements:
x |
breaks between intervals. |
P |
a matrix with n times d rows and k
columns. The ith row of P , P[i,] , contains the coefficients
for the polynomial over the ith interval, ordered from highest to
lowest. There must be one row for each interval in x. |
n |
number of intervals (length(x) - 1 ). |
k |
polynomial order. |
d |
number of polynomials. |
Original Octave version by Paul Kienzle pkienzle@user.sf.net. Conversion to R by Tom Short.
Fritsch, F. N. and Carlson, R. E., "Monotone Piecewise Cubic Interpolation," SIAM Journal of Numerical Analysis, vol. 17, pp.238-246, 1980.
Octave Forge http://octave.sf.net
xf = linspace(0,11,500); yf = sin(2*pi*xf/5) xp = c(0:10); yp = sin(2*pi*xp/5) pch = pchip(xp, yp, xf) plot(xp, yp, xlim=c(0,11)) lines(xf, pch, col = "orange")