interp.old {akima}  R Documentation 
Gridded Bivariate Interpolation for Irregular Data
Description
These functions implement bivariate interpolation onto a grid
for irregularly spaced input data. These functions are only for
backward compatibility, use interp
instead.
Usage
interp.old(x, y, z, xo= seq(min(x), max(x), length = 40),
yo=seq(min(y), max(y), length = 40), ncp = 0,
extrap=FALSE, duplicate = "error", dupfun = NULL)
interp.new(x, y, z, xo = seq(min(x), max(x), length = 40),
yo = seq(min(y), max(y), length = 40), linear = FALSE,
ncp = NULL, extrap=FALSE, duplicate = "error", dupfun = NULL)
Arguments
x 
vector of xcoordinates of data points or a

y 
vector of ycoordinates of data points. Missing values are not accepted. If left as NULL indicates that 
z 
vector of zcoordinates of data points or a character variable
naming the variable of interest in the
Missing values are not accepted.

xo 
vector of xcoordinates of output grid. The default is 40 points
evenly spaced over the range of 
yo 
vector of ycoordinates of output grid; analogous to

linear 
logical – indicating wether linear or spline
interpolation should be used. supersedes old 
ncp 
deprecated, use parameter old meaning was:
number of additional points to be used in computing partial
derivatives at each data point.

extrap 
logical flag: should extrapolation be used outside of the convex hull determined by the data points? 
duplicate 
character string indicating how to handle duplicate data points. Possible values are

dupfun 
a function, applied to duplicate points if

Details
see interp
Value
list with 3 components:
x , y 
vectors of x and y coordinates of output grid, the same as the input
argument 
z 
matrix of fitted zvalues. The value 
If input is a SpatialPointsDataFrame
a
SpatialPixelssDataFrame
is returned.
Note
interp.new
is deprecated and interp.old
will soon be
deprecated.
References
Akima, H. (1978). A Method of Bivariate Interpolation and Smooth Surface Fitting for Irregularly Distributed Data Points. ACM Transactions on Mathematical Software 4, 148164.
Akima, H. (1996). Algorithm 761: scattereddata surface fitting that has the accuracy of a cubic polynomial. ACM Transactions on Mathematical Software 22, 362–371.
See Also
contour
, image
,
approx
, spline
,
aspline
,
outer
, expand.grid
.