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)
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).
ConservationProblem) with the constraints
added to it.
See constraints for an overview of all functions for adding constraints.
# 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)
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