Add linear penalties
Add penalties to a conservation planning problem() to penalize
solutions that select planning units with higher values from a specific
data source (e.g. anthropogenic impact). These penalties assume
a linear trade-off between the penalty values and the primary
objective of the conservation planning problem() (e.g.
solution cost for minimum set problems; add_min_set_objective().
## S4 method for signature 'ConservationProblem,ANY,character' add_linear_penalties(x, penalty, data) ## S4 method for signature 'ConservationProblem,ANY,numeric' add_linear_penalties(x, penalty, data) ## S4 method for signature 'ConservationProblem,ANY,matrix' add_linear_penalties(x, penalty, data) ## S4 method for signature 'ConservationProblem,ANY,Matrix' add_linear_penalties(x, penalty, data) ## S4 method for signature 'ConservationProblem,ANY,Raster' add_linear_penalties(x, penalty, data) ## S4 method for signature 'ConservationProblem,ANY,dgCMatrix' add_linear_penalties(x, penalty, data)
x |
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penalty |
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data |
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This function penalizes solutions that have higher values according to the sum of the penalty values associated with each planning unit, weighted by status of each planning unit in the solution.
Specifically, the linear penalties are calculated using the following
equations.
Let I denote the set of planning units
(indexed by i), Z the set of management zones (indexed by
z), and Xiz the decision variable for allocating
planning unit i to zone z (e.g. with binary
values one indicating if planning unit is allocated or not). Also, let
P_z represent the penalty scaling value for zones
z in Z (argument to penalty), and
Diz the penalty data for allocating planning unit
i in I to zones z in Z (argument to
data if supplied as a matrix object).
sum_i^I sum_z^Z (Pz * Diz * Xiz)
Note that when the problem objective is to maximize some measure of benefit and not minimize some measure of cost, the term P_z is replaced with -P_z.
The argument to data can be specified using the following formats.
characterfield (column) name(s) that contain the data for
penalizing planning units. This type of argument is only
compatible if the planning units in the argument to x are a
Spatial, sf::sf(), or
data.frame object. The fields (columns) must have numeric
values, and must not contain any missing (NA) values.
For problems involving multiple zones, the argument to data must
contain a field name for each zone.
numericvector containing the data for penalizing
each planning unit. These values must not contain any missing
(NA) values. Note that this type of argument is only available
for planning units that contain a single zone.
Rastercontaining the data for
penalizing planning units. This type of argument is only
compatible if the planning units in the argument to x are
Spatial, sf::sf(), or
or Raster (i.e. they are in a spatially
referenced format).
If the planning unit data are a Spatial or
sf::sf() object, then the
penalty data are calculated by overlaying the planning units with
the argument to data and calculating the sum of the values.
If the planning unit data are in the
Raster then the penalty data are
calculated by extracting the cell values (note that the
planning unit data and the argument to codedata must have exactly
the same dimensionality, extent, and missingness).
For problems involving multiple zones, the argument to data must
contain a layer for each zone.
matrix, Matrix
containing numeric values
that specify data for penalizing each planning unit.
Each row corresponds to a planning unit, each column corresponds to a
zone, and each cell indicates the data for penalizing a planning unit
when it is allocated to a given zone.
# set seed for reproducibility
set.seed(600)
# load data
data(sim_pu_polygons, sim_pu_zones_stack, sim_features, sim_features_zones)
# add a column to contain the penalty data for each planning unit
# e.g. these values could indicate the level of habitat
sim_pu_polygons$penalty_data <- runif(nrow(sim_pu_polygons))
# plot the penalty data to visualise its spatial distribution
spplot(sim_pu_polygons, zcol = "penalty_data", main = "penalty data",
axes = FALSE, box = FALSE)
# create minimal problem with minimum set objective,
# this does not use the penalty data
p1 <- problem(sim_pu_polygons, sim_features, cost_column = "cost") %>%
add_min_set_objective() %>%
add_relative_targets(0.1) %>%
add_binary_decisions() %>%
add_default_solver(verbose = FALSE)
# print problem
print(p1)
# create an updated version of the previous problem,
# with the penalties added to it
p2 <- p1 %>% add_linear_penalties(100, data = "penalty_data")
# print problem
print(p2)
## Not run:
# solve the two problems
s1 <- solve(p1)
s2 <- solve(p2)
# plot the solutions and compare them,
# since we supplied a very high penalty value (i.e. 100), relative
# to the range of values in the penalty data and the objective function,
# the solution in s2 is very sensitive to values in the penalty data
spplot(s1, zcol = "solution_1", main = "solution without penalties",
axes = FALSE, box = FALSE)
spplot(s2, zcol = "solution_1", main = "solution with penalties",
axes = FALSE, box = FALSE)
# for real conservation planning exercises,
# it would be worth exploring a range of penalty values (e.g. ranging
# from 1 to 100 increments of 5) to explore the trade-offs
## End(Not run)
# now, let's examine a conservation planning exercise involving multiple
# management zones
# create targets for each feature within each zone,
# these targets indicate that each zone needs to represent 10% of the
# spatial distribution of each feature
targ <- matrix(0.1, ncol = number_of_zones(sim_features_zones),
nrow = number_of_features(sim_features_zones))
# create penalty data for allocating each planning unit to each zone,
# these data will be generated by simulating values
penalty_stack <- simulate_cost(sim_pu_zones_stack[[1]],
n = number_of_zones(sim_features_zones))
# plot the penalty data, each layer corresponds to a different zone
plot(penalty_stack, main = "penalty data", axes = FALSE, box = FALSE)
# create a multi-zone problem with the minimum set objective
# and penalties for allocating planning units to each zone,
# with a penalty scaling factor of 1 for each zone
p3 <- problem(sim_pu_zones_stack, sim_features_zones) %>%
add_min_set_objective() %>%
add_relative_targets(targ) %>%
add_linear_penalties(c(1, 1, 1), penalty_stack) %>%
add_binary_decisions() %>%
add_default_solver(verbose = FALSE)
# print problem
print(p3)
## Not run:
# solve problem
s3 <- solve(p3)
# plot solution
plot(category_layer(s3), main = "multi-zone solution",
axes = FALSE, box = FALSE)
## End(Not run)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.