VoxR (version 0.5.1)

surface: Compute the surface of density classes of a projection

Description

Compute the surface of density classes within a projection created by the project function and discretised by level. The surface is calculated using the following relationship : leveln

Usage

surface(data, method, levels, res, proportion)

Arguments

data

a data frame of a 2D point cloud containing : x, y coordinates of the pixels and the number of voxels (nvox), number of points (npts), ratio npts/nvox contained in each pixel

method

character string specifying the variable of interest of the projection : "nvox", "npts" or "ratio"

levels

a vector containing the discretisation levels as created by the level function

res

numeric definition of the resolution of the pixels. If res = 1, the calculated surface corresponds to the number of pixels.

proportion

logical : if TRUE the surfaces are expressed in proportion to the total surface

Value

A vector containing the surface of each density class

Details

Defaults :

• method = "nvox"
• res = 1
• proportion = FALSE

Examples

#- projection

data(treecloud_vox)
proj <- project(treecloud_vox,dim="xy")

#- creating vectors with interests variables

npts <- c(proj[,4])
nvox <- c(proj[,3])
ratio <- c(proj[,5])

#-creating level of discretisation

lev_vox <- level(nvox,by="quantiles",levels=c(0.2))
lev_pts <- level(npts,by="percents",levels=c(0.2,0.4,0.6,0.8))
lev_ratio <- c(1,2)# <- level(ratio,by="quantiles",level=c(0.25))

#- computing surfaces

surf_nvox <- surface(proj,method="nvox",levels=lev_vox,res=0.02,proportion=TRUE) 
surf_npts <- surface(proj,method="npts",levels=lev_pts,res=0.02,proportion=FALSE) 
surf_ratio <- surface(proj,method="ratio",levels=lev_ratio,res=1,proportion=FALSE) 
surf_nvox
surf_npts
surf_ratio