Piecewise cubic hermite interpolation
Piecewise cubic hermite interpolation.
pchip(x, y, xi = NULL)
x,y |
vectors giving the coordinates of the points to be
interpolated. |
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 |
number of intervals ( |
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 on Numerical Analysis, vol. 17, pp. 238-246, 1980.
Octave Forge http://octave.sf.net
xf <- seq(0, 11, length=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")
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