Package 'ipdw'

Generate a cost Raster

Description

Generate a cost raster from an object of class sf with point or polygon geometries

Usage

costrasterGen(xymat, pols, extent = "polys", projstr, resolution = 1)

Arguments

xymat	Matrix of coordinates or an sf object with point geometries
pols	sf object with polygon geometries
extent	Define extent based on extent of xymat/sf (points) or pols (polys). Default is polys.
projstr	proj4 string defining the output projection. A warning will be thrown if projstr does not match the projection of the extent target. Pass NULL for non-geographic grids.
resolution	Numeric defaults to 1. See raster.

Details

Ensure that the projection of the xymat coordinates and pols match. If they do not match use the st_transform command.

Value

RasterLayer

See Also

rasterize

Examples

## Not run: 
library(sf)
Sr1 <- st_polygon(list(cbind(c(0, 0, 1, 1, 0), c(0, 12, 12, 0, 0))))
Sr4 <- st_polygon(list(cbind(c(9, 9, 10, 10, 9), c(0, 12, 12, 0, 0))))
Sr2 <- st_polygon(list(cbind(c(1, 1, 9, 9, 1), c(11, 12, 12, 11, 11))))
Sr3 <- st_polygon(list(cbind(c(1, 1, 9, 9, 1), c(0, 1, 1, 0, 0))))
Sr5 <- st_polygon(list(cbind(c(4, 4, 5, 5, 4), c(4, 8, 8, 4, 4))))
pols <- st_as_sf(st_sfc(Sr1, Sr2, Sr3, Sr4, Sr5,
  crs = "+proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0"))

# using a matrix object
xymat <- matrix(3, 3, nrow = 1, ncol = 2)
costras <- costrasterGen(xymat, pols, projstr = NULL)

# plotting
plot(costras)
points(xymat)

## End(Not run)

---

Generate interpolation error stats from validation datasets

Description

Generate error statistics from validation point datasets overlaid on a raster surface

Usage

errorGen(
  finalraster,
  validation.sf_ob,
  validation.data,
  plot = FALSE,
  title = ""
)

Arguments

finalraster	RasterLayer object
validation.sf_ob	sf object with points geometry
validation.data	data.frame
plot	logical. Plot comparison?
title	Plot labels

Value

List of error statistics

Examples

library(sf)
validation.data <- data.frame(rnorm(10, mean = 0.2, sd = 1))
names(validation.data) <- c("validation")
validation.sf_ob <- validation.data
validation.data <- as.numeric(unlist(validation.data))
xy <- data.frame(x = c(0:9), y = rep(1, 10))
validation.sf_ob <- st_as_sf(cbind(validation.sf_ob, xy), coords = c("x", "y"))

m <- matrix(NA, 1, 10)
out.ras <- raster(m, xmn = 0, xmx = ncol(m), ymn = 0, ymx = nrow(m))
out.ras[] <- validation.data + rnorm(ncell(out.ras), mean = 0.01, sd = 0.2)

valid.stats <- errorGen(out.ras, validation.sf_ob, validation.data, plot = TRUE,
  title = "Validation Plot")
valid.stats

---

Inverse Path Distance Weighting

Description

Interpolate geo-referenced point data using inverse path distance weighting.

Usage

ipdw(
  sf_ob,
  costras,
  range,
  paramlist,
  overlapped = FALSE,
  yearmon = "default",
  removefile = TRUE,
  step = 16,
  dist_power = 1,
  trim_rstack = FALSE
)

Arguments

sf_ob	sf object with point geometries
costras	RasterLayer. Cost raster
range	numeric. Range of interpolation neighborhood
paramlist	character. String representing parameter names
overlapped	logical. Default is FALSE, specify TRUE if some points lie on top of barriers
yearmon	character. String specifying the name of the sf_ob
removefile	logical. Remove files after processing?
step	numeric. Number of sub loops to manage memory during raster processing.
dist_power	numeric. Distance decay power (p)
trim_rstack	logical. Trim the raster output by the convex hill of sf_ob

Details

This is a high level function that interpolates an sf object with point geometries in a single pass.

Points must be located within a single contiguous area. The presence of "landlocked" points will cause errors. It may be necessary to increase the value assigned to land areas when using a large range value in combination with a large sized cost rasters (grain x extent). In these cases, the value of land areas should be increased to ensure that it is always greater than the maximum accumulated cost path distance of any given geo-referenced point.

Value

RasterLayer

Examples

# see vignette

---

Inverse Distance Weighting with custom distances

Description

This function takes a rasterstack of pathdistances and generates surfaces by weighting parameter values by these distances

Usage

ipdwInterp(
  sf_ob,
  rstack,
  paramlist,
  overlapped = FALSE,
  yearmon = "default",
  removefile = TRUE,
  dist_power = 1,
  trim_rstack = FALSE
)

Arguments

sf_ob	sf object with point geometries
rstack	RasterStack of path distances
paramlist	character. String representing parameter names
overlapped	logical. Default is FALSE, specify TRUE if some points lie on top of barriers
yearmon	character. String specifying the name of the sf object
removefile	logical. Remove files after processing?
dist_power	numeric. Distance decay power (p)
trim_rstack	logical. Trim the raster stack by the convex hull of sf_ob

Details

Under the hood, this function evaluates:

$V = \frac{\sum\limits_{i=1}^n v_i \frac{1}{d_i^p}}{\sum\limits_{i=1}^n \frac{1}{d_i^p}}$

where d is the distance between prediction and measurement points, v_i is the measured parameter value, and p is a power parameter.

Value

RasterLayer

Examples

library(sf)
sf_ob <- data.frame(rnorm(2))
xy    <- data.frame(x = c(4, 2), y = c(8, 4))
sf_ob <- st_as_sf(cbind(sf_ob, xy), coords = c("x", "y"))

m <- matrix(NA, 10, 10)
costras <- raster(m, xmn = 0, xmx = ncol(m), ymn = 0, ymx = nrow(m))

# introduce spatial gradient
costras[] <- runif(ncell(costras), min = 1, max = 10)
for (i in 1:nrow(costras)) {
  costras[i, ] <- costras[i, ] + i
  costras[, i] <- costras[, i] + i
}

rstack <- pathdistGen(sf_ob, costras, 100, progressbar = FALSE)
final.raster <- ipdwInterp(sf_ob, rstack, paramlist = c("rnorm.2."), overlapped = TRUE)
plot(final.raster)
plot(sf_ob, add = TRUE)

---

Generate a stack of path distance raster objects

Description

Generate a stack of path accumulated distance raster objects

Usage

pathdistGen(sf_ob, costras, range, yearmon = "default", progressbar = TRUE)

Arguments

sf_ob	sf object with point geometries
costras	RasterLayer cost raster
range	numeric. Range of interpolation neighborhood
yearmon	character. String specifying the name of the sf_ob
progressbar	logical show progressbar during processing?

Value

RasterStack object of path distances

Examples

library(sf)
sf_ob <- data.frame(rnorm(2))
xy   <- data.frame(x = c(4, 2), y = c(8, 4))
sf_ob <- st_as_sf(cbind(sf_ob, xy), coords = c("x", "y"))

m <- matrix(NA, 10, 10)
costras <- raster(m, xmn = 0, xmx = ncol(m), ymn = 0, ymx = nrow(m))
costras[] <- runif(ncell(costras), min = 1, max = 10)
# introduce spatial gradient
for (i in 1:nrow(costras)) {
  costras[i, ] <- costras[i, ] + i
  costras[, i] <- costras[, i] + i
}

rstack <- pathdistGen(sf_ob, costras, 100, progressbar = FALSE)

---

Remove NA points features and drop corresponding raster stack layers

Description

Remove NA points features and drop corresponding raster stack layers

Usage

rm_na_pointslayers(param_name, sf_ob, rstack)

Arguments

param_name	character name of data column
sf_ob	sf object with point geometries
rstack	RasterStack or RasterBrick

---