Bilinear and Bicubic Interpolation to Grid
This code includes a bicubic interpolation and a bilinear interpolation adapted from Numerical Recipes in C: The art of scientific computing (chapter 3... bicubic interpolation) and a bicubic interpolation from in java code.
Inputs are a list of points to interpolate to and from raster objects of class 'asc' (adehabitat package), 'RasterLayer' (raster package) or 'SpatialGridDataFrame' (sp package).
interp2grid(mat,xout,yout,xin=NULL,yin=NULL,type=2)
mat |
a matrix of data that can be a raster matrix of class 'asc' (adehabitat package), 'RasterLayer' (raster package) or 'SpatialGridDataFrame' (sp package) NA values are not permitted.. data must be complete. |
xout |
a vector of data representing x coordinates of the output grid. Resulting grid must have square cell sizes if mat is of class 'asc', 'RasterLayer' or 'SpatialGridDataFrame'. |
yout |
a vector of data representing x coordinates of the output grid. Resulting grid must have square cell sizes if mat is of class 'asc', 'RasterLayer' or 'SpatialGridDataFrame'. |
xin |
a vector identifying the locations of the columns of the input data matrix. These are automatically populated if mat is of class 'asc', 'RasterLayer' or 'SpatialGridDataFrame'. |
yin |
a vector identifying the locations of the rows of the input data matrix. These are automatically populated if mat is of class 'asc', 'RasterLayer' or 'SpatialGridDataFrame'. |
type |
an integer value representing the type of interpolation method used. 1 - bilinear adapted from Numerical Recipes in C 2 - bicubic adapted from Numerical Recipes in C 3 - bicubic adapted from online java code |
Returns a matrix of the originating class.
Jeremy VanDerWal jjvanderwal@gmail.com
tx = seq(0,3,0.1)
ty = seq(0,3,0.1)
tmat = matrix(runif(16,1,16),nrow=4)
txin = seq(0,3,length=4)
tyin = seq(0,3,length=4)
bilinear1 = interp2grid(tmat,tx,ty,txin, tyin, type=1)
bicubic2 = interp2grid(tmat,tx,ty,txin, tyin, type=2)
bicubic3 = interp2grid(tmat,tx,ty,txin, tyin, type=3)
par(mfrow=c(2,2),cex=1)
image(tmat,main='base',zlim=c(0,16),col=heat.colors(100))
image(bilinear1,main='bilinear',zlim=c(0,16),col=heat.colors(100))
image(bicubic2,main='bicubic2',zlim=c(0,16),col=heat.colors(100))
image(bicubic3,main='bicubic3',zlim=c(0,16),col=heat.colors(100))Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.