interp2grid: Bilinear and Bicubic Interpolation to Grid

In jjvanderwal/climates: Methods for working with weather & climate

Description

This code was includes bicubic interpolation and bilinear interpolation adapted from Numerical Recipes in C: The are of scientific computing http://www.nrbook.com/nr3/ (chapter 3... bicubic interpolation) and a bicubic interpolation from http://www.paulinternet.nl/?page=bicubic in java code.

Inputs are a list of points representing grid coordinates to interpolate to from raster objects of class 'asc' (adehabitat package), 'RasterLayer' (raster package) or 'SpatialGridDataFrame' (sp package).

Usage

interp2grid(mat, xout, yout, xin = NULL, yin = NULL, type = 2)

Arguments

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

Value

Returns a matrix of the originating class.

Author(s)

Jeremy VanDerWal [e-mail]

See Also

interp2pnt

Examples

## Not run: 

#create some data
tx = seq(0,3,0.1)
ty = seq(0,3,0.1)

#create a matrix
tmat = matrix(runif(16,1,16),nr=4)

#do the interpolations
bilinear1 = interp2grid(tmat,tx,ty,type=1)
bicubic2 = interp2grid(tmat,tx,ty,type=2)
bicubic3 = interp2grid(tmat,tx,ty,type=3)

#show the plots
#png(filename = "trials1.png",width=480*4,height=480*4,pointsize=20)
	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))
#dev.off()

## End(Not run)

jjvanderwal/climates documentation built on May 19, 2019, 11:41 a.m.