Add semi-continuous decisions

Add a semi-continuous decision to a conservation planning problem. This is a relaxed decision where a part of a planning unit can be prioritized, as opposed to the entire planning unit. This decision is similar to the add_proportion_decisions() function, except that it has an upper bound parameter. By default, the decision can range from prioritizing none (0%) to all (100%) of a planning unit. However, an upper bound can be specified to ensure that, at most, only a fraction (e.g., 80%) of a planning unit can be prioritized. This type of decision may be useful when it is not practical to conserve entire planning units.

Usage

add_semicontinuous_decisions(x, upper_limit)

Arguments

x

problem() object.

upper_limit

numeric value specifying the maximum proportion of a planning unit that can be reserved (e.g., set to 0.8 for 80%).

Value

An updated problem() object with the decisions added to it.

Details

Conservation planning problems involve making decisions on planning units. These decisions are then associated with actions (e.g., turning a planning unit into a protected area). Only a single decision should be added to a problem() object. Note that if multiple decisions are added to an object, then the last one to be added will be used during optimization. Also, if no decision is added to a problem(), then this decision will be used by default.

See also

See decisions for an overview of all functions for adding decisions.

Other decisions: add_binary_decisions(), add_proportion_decisions()

Examples

# set seed for reproducibility
set.seed(500)

# load data
sim_pu_raster <- get_sim_pu_raster()
sim_features <- get_sim_features()
sim_zones_pu_raster <- get_sim_zones_pu_raster()
sim_zones_features <- get_sim_zones_features()

# create minimal problem with semi-continuous decisions
p1 <-
  problem(sim_pu_raster, sim_features) %>%
  add_min_set_objective() %>%
  add_relative_targets(0.1) %>%
  add_semicontinuous_decisions(0.5) %>%
  add_default_solver(verbose = FALSE)

# solve problem
s1 <- solve(p1)

# plot solutions
plot(s1, main = "solution", axes = FALSE)


# build multi-zone conservation problem with semi-continuous decisions
p2 <-
  problem(sim_zones_pu_raster, sim_zones_features) %>%
  add_min_set_objective() %>%
  add_relative_targets(matrix(runif(15, 0.1, 0.2), nrow = 5, ncol = 3)) %>%
  add_semicontinuous_decisions(0.5) %>%
  add_default_solver(verbose = FALSE)

# solve the problem
s2 <- solve(p2)

# print solution
print(s2)
#> class       : SpatRaster
#> size        : 10, 10, 3  (nrow, ncol, nlyr)
#> resolution  : 0.1, 0.1  (x, y)
#> extent      : 0, 1, 0, 1  (xmin, xmax, ymin, ymax)
#> coord. ref. : WGS 84 / Pseudo-Mercator (EPSG:3857)
#> source(s)   : memory
#> varnames    : sim_zones_pu_raster
#>               sim_zones_pu_raster
#>               sim_zones_pu_raster
#> names       : zone_1, zone_2, zone_3
#> min values  :      0,      0,      0
#> max values  :    0.5,    0.5,    0.5

# plot solution
# panels show the proportion of each planning unit allocated to each zone
plot(s2, axes = FALSE)