fix bug in greedy_heuristic_prioritization() feasibility calculations (…

…#54) - Fix bug in `greedy_heuristic_algorithm()` function so that it returns a solution if it is not possible to select enough planning units to meet the target for any species. Instead of throwing an error, it will now throw a warning and return a solution containing the cheapest set of planning units within the budget and locked out constraints. Note that this solution will have an objective value of zero, because it has zero probability of meeting any of the species' targets.
prioritizr · Jul 24, 2024 · f733008 · f733008
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diff --git a/DESCRIPTION b/DESCRIPTION
@@ -1,6 +1,6 @@
 Package: surveyvoi
 Type: Package
-Version: 1.1.0.0
+Version: 1.1.0.1
 Title: Survey Value of Information
 Description: Decision support tool for prioritizing sites for ecological
     surveys based on their potential to improve plans for conserving

diff --git a/NEWS.md b/NEWS.md
@@ -1,3 +1,13 @@
+# surveyvoi 1.1.0.1
+
+- Fix bug in `greedy_heuristic_algorithm()` function so that it returns a
+  solution if it is not possible to select enough planning units to meet the
+  target for any species. Instead of throwing an error, it will now throw a
+  warning and return a solution containing the cheapest set of planning units
+  within the budget and locked out constraints. Note that this solution
+  will have an objective value of zero, because it has zero probability of
+  meeting any of the species' targets.
+
 # surveyvoi 1.1.0.0
 
 - New `greedy_heuristic_algorithm()` function that can be used to generate

diff --git a/R/greedy_heuristic_optimization.R b/R/greedy_heuristic_optimization.R
@@ -142,15 +142,36 @@ greedy_heuristic_prioritization <- function(
     site_management_locked_out <- rep(FALSE, nrow(site_data))
   }
 
-  ## validate that targets are feasible given budget and locked out units
-  sorted_costs <- sort(
-    site_data[[site_management_cost_column]][!site_management_locked_out])
-  sorted_costs <- sorted_costs[
-    seq_len(max(feature_data[[feature_target_column]]))]
-  assertthat::assert_that(
-    sum(sorted_costs) <= total_budget,
-    msg = paste("targets cannot be achieved given budget and locked out",
-                "planning units"))
+  ## validate it is possible to select enough planning units to meet
+  ## the target for even a single feature,
+  ## if not, then it's not possible to generate a single solution
+  ## with an objective value = 0
+  cheapest_sol <- rep(FALSE, nrow(site_data))
+  cheapest_sol[site_management_locked_in] <- TRUE
+  if (min(feature_data[[feature_target_column]]) > sum(cheapest_sol)) {
+    idx <- which(!site_management_locked_out & !site_management_locked_in)
+    idx_costs <- site_data[[site_management_cost_column]]
+    idx_costs <- idx_costs[idx]
+    idx_order <- order(idx_costs)
+    idx_add <- cumsum(idx_costs[idx_order]) <= total_budget
+    sel_idx <- idx[idx_order[which(idx_add)]]
+    cheapest_sol[sel_idx] <- TRUE
+  }
+  if (
+    sum(cheapest_sol) < min(feature_data[[feature_target_column]])
+  ) {
+    ### throw warning
+    warning(
+      paste(
+        "it is not possible to select enough planning units to meet",
+        "any targets for even a single feature",
+        "(given the budget and locked out planning units)"
+      ),
+      call. = TRUE, immediate. = FALSE
+    )
+    ## return solution
+    return(list(x = cheapest_sol, objval = 0))
+  }
 
   # create prior data
   prior_data <-

diff --git a/docs/404.html b/docs/404.html
diff --git a/docs/articles/index.html b/docs/articles/index.html
diff --git a/docs/articles/surveyvoi.html b/docs/articles/surveyvoi.html
diff --git a/docs/authors.html b/docs/authors.html
diff --git a/docs/index.html b/docs/index.html
diff --git a/docs/news/index.html b/docs/news/index.html
diff --git a/docs/pkgdown.yml b/docs/pkgdown.yml
@@ -3,7 +3,7 @@ pkgdown: 2.0.7
 pkgdown_sha: ~
 articles:
   surveyvoi: surveyvoi.html
-last_built: 2024-07-09T23:25Z
+last_built: 2024-07-24T01:59Z
 urls:
   reference: https://github.com/prioritizr/surveyvoi/reference
   article: https://github.com/prioritizr/surveyvoi/articles

diff --git a/docs/reference/approx_evdsi.html b/docs/reference/approx_evdsi.html
diff --git a/docs/reference/approx_near_optimal_survey_scheme.html b/docs/reference/approx_near_optimal_survey_scheme.html
diff --git a/docs/reference/approx_optimal_survey_scheme.html b/docs/reference/approx_optimal_survey_scheme.html
diff --git a/docs/reference/env_div_survey_scheme.html b/docs/reference/env_div_survey_scheme.html
diff --git a/docs/reference/evdci.html b/docs/reference/evdci.html
diff --git a/docs/reference/evdsi.html b/docs/reference/evdsi.html
diff --git a/docs/reference/feasible_survey_schemes.html b/docs/reference/feasible_survey_schemes.html
diff --git a/docs/reference/fit_hglm_occupancy_models.html b/docs/reference/fit_hglm_occupancy_models.html
diff --git a/docs/reference/fit_xgb_occupancy_models.html b/docs/reference/fit_xgb_occupancy_models.html
diff --git a/docs/reference/geo_cov_survey_scheme.html b/docs/reference/geo_cov_survey_scheme.html
diff --git a/docs/reference/greedy_heuristic_prioritization.html b/docs/reference/greedy_heuristic_prioritization.html
diff --git a/docs/reference/index.html b/docs/reference/index.html
diff --git a/docs/reference/n_states.html b/docs/reference/n_states.html
diff --git a/docs/reference/optimal_survey_scheme.html b/docs/reference/optimal_survey_scheme.html
diff --git a/docs/reference/prior_probability_matrix.html b/docs/reference/prior_probability_matrix.html
diff --git a/docs/reference/relative_site_richness_scores.html b/docs/reference/relative_site_richness_scores.html
diff --git a/docs/reference/relative_site_uncertainty_scores.html b/docs/reference/relative_site_uncertainty_scores.html
diff --git a/docs/reference/sim_data.html b/docs/reference/sim_data.html
diff --git a/docs/reference/simulate_feature_data.html b/docs/reference/simulate_feature_data.html
diff --git a/docs/reference/simulate_site_data.html b/docs/reference/simulate_site_data.html
diff --git a/docs/reference/surveyvoi.html b/docs/reference/surveyvoi.html
diff --git a/docs/reference/weighted_survey_scheme.html b/docs/reference/weighted_survey_scheme.html
diff --git a/inst/doc/surveyvoi.html b/inst/doc/surveyvoi.html
@@ -12,7 +12,7 @@
 
 <meta name="author" content="Jeffrey O. Hanson" />
 
-<meta name="date" content="2024-07-10" />
+<meta name="date" content="2024-07-24" />
 
 <title>surveyvoi: Survey Value of Information</title>
 
@@ -171,7 +171,7 @@
 
 <h1 class="title toc-ignore">surveyvoi: Survey Value of Information</h1>
 <h4 class="author">Jeffrey O. Hanson</h4>
-<h4 class="date">2024-07-10</h4>
+<h4 class="date">2024-07-24</h4>
 
 
 <div id="TOC">