Interpolation
Interpolation methods, including linear, spline, and cubic interpolation.
interp1(x, y, xi, method = c("linear", "nearest", "pchip", "cubic", "spline"),
extrap = NA, ...)x,y |
vectors giving the coordinates of the points to be
interpolated. |
xi |
points at which to interpolate. |
method |
one of |
extrap |
if |
... |
for |
The following methods of interpolation are available:
'nearest': return nearest neighbour
'linear': linear interpolation from nearest neighbours
'pchip': piecewise cubic hermite interpolating polynomial
'cubic': cubic interpolation from four nearest neighbours
'spline': cubic spline interpolation–smooth first and second
derivatives throughout the curve
The interpolated signal, an array of length(xi).
Original Octave version by Paul Kienzle pkienzle@user.sf.net. Conversion to R by Tom Short.
Octave Forge http://octave.sf.net
xf <- seq(0, 11, length=500) yf <- sin(2*pi*xf/5) #xp <- c(0:1,3:10) #yp <- sin(2*pi*xp/5) xp <- c(0:10) yp <- sin(2*pi*xp/5) extrap <- TRUE lin <- interp1(xp, yp, xf, 'linear', extrap = extrap) spl <- interp1(xp, yp, xf, 'spline', extrap = extrap) pch <- interp1(xp, yp, xf, 'pchip', extrap = extrap) cub <- interp1(xp, yp, xf, 'cubic', extrap = extrap) near <- interp1(xp, yp, xf, 'nearest', extrap = extrap) plot(xp, yp, xlim = c(0, 11)) lines(xf, lin, col = "red") lines(xf, spl, col = "green") lines(xf, pch, col = "orange") lines(xf, cub, col = "blue") lines(xf, near, col = "purple")
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