leastcostpath - version 1.8.0 Build Status CRAN status CRAN Downloads Month CRAN Downloads Total =============================

The R library leastcostpath provides the functionality to calculate Cost Surfaces based on multiple cost functions that approximate the difficulty of moving across a landscape. Furthermore, the attraction/repulsion of landscape features can be incorporated into the Cost Surfaces, as well as barriers that inhibit movement.

NOTE: The R library leastcostpath requires the use of projected coordinate systems. The package does not account for geographic coordinate systems.

Cost Surfaces can be used to calculate Least Cost Paths, which are often, but not exclusively, used in archaeological research. leastcostpath also provides the functionality to calculate movement potential within a landscape through the implementation of From-Everywhere-to-Everywhere (FETE) (White and Barber, 2012), Cumulative Cost Paths (Verhagen, 2013), and Least Cost Path calculation within specified distance bands (Llobera, 2015). Furthermore, the library allows for the calculation of stochastic least cost paths and wide least cost paths.

Lastly, the library provides functionality to validate the accuracy of computed Least Cost Paths relative to another path.

This package is built on classes and functions provided in the R package gdistance (Van Etten, 2017).

Functions currently in development: * force_isotropy()

Functions recently added: * create_distance_cs()

Getting Started

Installation

#install.packages("devtools")
library(devtools)
install_github("josephlewis/leastcostpath")
library(leastcostpath)

Usage

Creation of Cost Surfaces

library(leastcostpath)
r <- raster::raster(system.file('external/maungawhau.grd', package = 'gdistance'))
    
slope_cs <- create_slope_cs(r, cost_function = 'tobler')
slope_cs_10 <- create_slope_cs(r, cost_function = 'tobler', max_slope = 10)
slope_cs_exagg <- create_slope_cs(r, cost_function = 'tobler', exaggeration = TRUE)

distance_cs <- create_distance_cs(r, neighbours = 16)

Least Cost Path computation

loc1 = cbind(2667670, 6479000)
loc1 = sp::SpatialPoints(loc1)

loc2 = cbind(2667800, 6479400)
loc2 = sp::SpatialPoints(loc2)

lcps <- create_lcp(cost_surface = slope_cs, origin = loc1, destination = loc2, directional = FALSE)

plot(raster(slope_cs))
plot(lcps[1,], add = T, col = "red") # location 1 to location 2
plot(lcps[2,], add = T, col = "blue") # location 2 to location 1

Cost Corridors

cc <- create_cost_corridor(slope_cs, loc1, loc2)

plot(cc)
plot(loc1, add = T)
plot(loc2, add = T)

From-Everywhere-to-Everywhere Least Cost Paths

locs <- sp::spsample(as(raster::extent(r), 'SpatialPolygons'),n=10,'regular')

lcp_network <- create_FETE_lcps(cost_surface = slope_cs, locations = locs,
cost_distance = FALSE, parallel = FALSE)

plot(raster(slope_cs))
plot(locs, add = T)
plot(lcp_network, add = T)

Cumulative Cost Paths

locs <- sp::spsample(as(raster::extent(r), 'SpatialPolygons'),n=1,'random')

lcp_network <- create_CCP_lcps(cost_surface = slope_cs, location = locs, distance = 50,
radial_points = 10, cost_distance = FALSE, parallel = FALSE)

plot(raster(slope_cs))
plot(locs, add = T)
plot(lcp_network, add = T)

Banded Least Cost Paths

locs <- sp::spsample(as(raster::extent(r), 'SpatialPolygons'),n=1,'random')

lcp_network <- create_banded_lcps(cost_surface = slope_cs, location = locs, min_distance = 20,
max_distance = 50, radial_points = 10, cost_distance = FALSE, parallel = FALSE)

plot(raster(slope_cs))
plot(locs, add = T)
plot(lcp_network, add = T)

Least Cost Path Density

cumulative_lcps <- create_lcp_density(lcps = lcp_network, raster = r, rescale = FALSE)

plot(cumulative_lcps)

Least Cost Path Network

locs <- sp::spsample(as(raster::extent(r), 'SpatialPolygons'),n=5,'regular')

mat <- cbind(c(1, 4, 2, 1), c(2, 2, 4, 3))

lcp_network <- create_lcp_network(slope_cs, locations = locs, 
nb_matrix = mat, cost_distance = FALSE, parallel = FALSE)

Stochastic Least Cost Path

locs <- sp::spsample(as(raster::extent(r), 'SpatialPolygons'),n=2,'random')

stochastic_lcp <- replicate(n = 10, create_stochastic_lcp(cost_surface = slope_cs,
origin = locs[1,], destination = locs[2,], directional = FALSE))

stochastic_lcp <- do.call(rbind, stochastic_lcp)

Probabilistic Least Cost Path

locs <- sp::spsample(as(raster::extent(r), 'SpatialPolygons'),n=2,'random')

RMSE <- 5
n <- 10
lcps <- list()

for (i in 1:n) {

lcps[[i]] <- leastcostpath::create_lcp(cost_surface = leastcostpath::create_slope_cs(dem = leastcostpath::add_dem_error(dem = r, rmse = RMSE, type = "autocorrelated"), cost_function = "tobler", neighbours = 16), origin = locs[1,], destination = locs[2,], directional = FALSE, cost_distance = TRUE)

}

lcps <- do.call(rbind, lcps)

Wide Least Cost Path

n <- 3

slope_cs <- create_slope_cs(r, cost_function = 'tobler', neighbours = wide_path_matrix(n))

loc1 = cbind(2667670, 6479000)
loc1 = sp::SpatialPoints(loc1)

loc2 = cbind(2667800, 6479400)
loc2 = sp::SpatialPoints(loc2)

lcps <- create_wide_lcp(cost_surface = slope_cs, origin = loc1,
destination = loc2, path_ncells = n)

Common Errors

Error in if (is.numeric(v) && any(v < 0)) { : 
missing value where TRUE/FALSE needed

Error caused when trying to calculate a Least Cost Path using SpatialPoints outside of the Cost Surface Extent * Check SpatialPoints used in the LCP calculation coincide with Raster / Cost Surface * Check coordinate systems of the Raster/Cost Surface is the same as the SpatialPoints

```Error in get.shortest.paths(adjacencyGraph, indexOrigin, indexGoal):```
```At structural_properties.c:4521 :```
```Weight vector must be non-negative, Invalid value```

Error caused when calculating a Least Cost Path using a Cost Surface that contains negative values. Error due to Djikstra’s algorithm requiring non-negative values * Check if there are negative values via:

  ```quantile(*your_cost_surface*@transitionMatrix@x)```
  

Contributing

If you would like to contribute to the R Package leastcostpath, please follow the “fork-and-pull” Git workflow:

  1. Fork the rep on Github
  2. Clone the project to your own machine
  3. Commit the changes to your own branch
  4. Push your work back to your fork
  5. Submit a pull request so that the changes can be reviewed

Issues

Please submit issues and enhancement requests via github Issues * If submitting an issue, please clearly describe the issue, including steps to reproduce when it is a bug, or a justification for the proposed enhancement request

Case Studies Using leastcostpath

Lewis, J. Probabilistic Modelling using Monte Carlo Simulation for Incorporating Uncertainty in Least Cost Path Results: a Roman Road Case Study, Peer Community in Archaeology, 100005. 10.24072/pci.archaeo.100005

Ludwig, B. Reconstructing the Ancient Route Network in Pergamon’s Surroundings. Land 2020, 9, 241. https://doi.org/10.3390/land9080241

Versioning

See NEWS.md for a summary of Version updates

Authors

Citation

Please cite as:

Lewis, J. (2020) leastcostpath: Modelling Pathways and Movement Potential Within a Landscape (version 1.8.0). 
Available at: https://cran.r-project.org/web/packages/leastcostpath/index.html