swfscMisc (version 1.7)

catSpatInterp: Categorical Spatial Interpolation

Description

Create a raster of probability of categorical values interpolated across a 2-dimensional space given a set of points where each is assigned to one of several classes.

Usage

catSpatInterp(
  data,
  x.col = "x",
  y.col = "y",
  group.col = "group",
  num.grid = 100,
  knn = 10,
  hull.buffer = 0.1,
  num.cores = 1,
  num.batches = NULL
)

Value

A list containing a raster and points of buffered convex hull.

Arguments

data

matrix or data.frame containing points and grouping designation.

x.col, y.col, group.col

numbers or characters identifying which columns in data are the x and y values and grouping designation.

num.grid

number of grid cells for k-nearest neighbor interpolation.

knn

number of nearest neighbors to consider for interpolation.

hull.buffer

percent increase of convex hull to use as spatial area to interpolate over.

num.cores

number of cores to distribute interpolations over.

num.batches

number of batches to divide grid cell interpolations into.

Author

Eric Archer

References

Adapted from code originally presented in a blog post on Categorical Spatial Interpolation by Timo Grossenbacher https://timogrossenbacher.ch/2018/03/categorical-spatial-interpolation-with-r/

Examples

if (FALSE) {
iris.mds <- stats::cmdscale(dist(iris[, 1:4]), k = 2)
mds.df <- setNames(
  cbind(iris.mds, data.frame(iris$Species)),
  c("dim1", "dim2", "Species")
)

result <- catSpatInterp(
  mds.df, x.col = "dim1", y.col = "dim2", group.col = "Species", 
  num.grid = 300, knn = 20, hull.buffer = 0.05,
  num.cores = 5, num.batches = NULL
)

library(ggplot2)
ggplot(mapping = aes(dim1, dim2)) +
  geom_raster(
    aes(fill = Species, alpha = prob), 
    data = result$raster
  ) +
  geom_polygon(data = result$hull.poly, fill = NA, col = "black") +
  geom_hline(yintercept = 0, col = "white") +
  geom_vline(xintercept = 0, col = "white") +
  geom_point(
    aes(fill = Species), 
    data = mds.df, 
    col = "black", 
    shape = 21, 
    size = 4
  ) + 
  theme(
    axis.ticks = element_blank(),
    axis.text = element_blank(),
    axis.title = element_blank(),
    legend.position = "top",
    panel.grid = element_blank(),
    panel.background = element_blank()
  )
}