Add mandatory allocation constraints
Add constraints to ensure that every planning unit is allocated to a management zone in the solution. Note that this function can only be used with problems that contain multiple zones.
## S4 method for signature 'ConservationProblem' add_mandatory_allocation_constraints(x)
x |
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For a conservation planning problem() with multiple
management zones, it may sometimes be desirable to obtain a solution that
assigns each and every single planning unit to a zone. For example, when
developing land-use plans, some decision makers may require that each and
every single parcel of land has been allocated a specific land-use type.
In other words are no "left over" areas. Although it might seem tempting
to simply solve the problem and manually assign "left over" planning units
to a default zone afterwards (e.g. an "other", "urban", or "grazing"
land-use), this could result in highly sub-optimal solutions if there
penalties for siting the default land-use adjacent to other zones.
Instead, this function can be used to specify that all planning units in a
problem with multiple zones must be allocated to a management zone (i.e.
zone allocation is mandatory).
Object (i.e. ConservationProblem) with the constraints
added to it.
# set seed for reproducibility
set.seed(500)
# load data
data(sim_pu_zones_stack, sim_features_zones)
# create multi-zone problem with minimum set objective
targets_matrix <- matrix(rpois(15, 1), nrow = 5, ncol = 3)
# create minimal problem with minimum set objective
p1 <- problem(sim_pu_zones_stack, sim_features_zones) %>%
add_min_set_objective() %>%
add_absolute_targets(targets_matrix) %>%
add_binary_decisions() %>%
add_default_solver(verbose = FALSE)
# create another problem that is the same as p1, but has constraints
# to mandate that every planning unit in the solution is assigned to
# zone
p2 <- p1 %>% add_mandatory_allocation_constraints()
## Not run:
# solve problems
s1 <- solve(p1)
s2 <- solve(p2)
# convert solutions into category layers, where each pixel is assigned
# value indicating which zone it was assigned to in the zone
c1 <- category_layer(s1)
c2 <- category_layer(s2)
# plot solution category layers
plot(stack(c1, c2), main = c("default", "mandatory allocation"),
axes = FALSE, box = FALSE)
## End(Not run)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.