change to avoid division by 0

data/factor_chart.tsv

@@ -1,5 +1,5 @@
 experimental_unit	factor_name	factor_description	role_in_simulation	min_level	max_level	other_constraints
-realm	initial_ proportion_not_desert	This is the initial proportion of ecoregions within the realm which are currently within a biome of “Deserts & Xeric Shrublands” but  were historically within a different biome.  This accounts for desertification.	The map used is based on current biomes. However, the simulation starts with some of the ecoregions currently within desert biomes possibly being any kind of grassland, “Temperate Broadleaf & Mixed Forests” or “Temperate Conifer Forests”. As the simulation progresses, these can switch to present-day desert.	0	1	none
+realm	initial_proportion_not_desert	This is the initial proportion of ecoregions within the realm which are currently within a biome of “Deserts & Xeric Shrublands” but  were historically within a different biome.  This accounts for desertification.	The map used is based on current biomes. However, the simulation starts with some of the ecoregions currently within desert biomes possibly being any kind of grassland, “Temperate Broadleaf & Mixed Forests” or “Temperate Conifer Forests”. As the simulation progresses, these can switch to present-day desert.	0	1	none
 realm	initial_pop_density_of_desert	This is the initial population density per square mile in deserts within the realm.	These densities are later converted to actual numbers of people.	0	0.3	
 realm	initial_pop_density_of_tundra	This is the initial population density per square mile in tundra within the realm.	These densities are later converted to actual numbers of people.	0	0.3	
 realm/biome combo	initial_pop_density_ratio	This is the ratio of the initial population density per square mile in a biome within the realm to the mean of initial_pop_density_of_desert and initial_pop_density_of_tundra.	This is used to set the initial_pop_density for each biome/realm combination (with the exception of combinations containing desert or tundra).	1	1000	

data/planning_matrix.txt

@@ -1,4 +1,4 @@
-"earth" "location" "REALM" "BIOME_NAME" "ECO_NAME" "initial_agricultural_tech_level_in_use" "initial_healthcare_tech_level_in_use" "initial_housing_tech_level_in_use" "initial_transportation_tech_level_in_use" "initial_unaided_d_max_pop_density" "initial_unaided_not_dt_max_pop_density" "initial_unaided_t_max_pop_density" "initial_warfare_tech_level_in_use" "relevance_of_dist_based_on_transportation_tech_level" "initial_ proportion_not_desert" "initial_pop_density_of_desert" "initial_pop_density_of_tundra" "initial_pop_density_ratio" "initial_transition_probability_to_desert"
+"earth" "location" "REALM" "BIOME_NAME" "ECO_NAME" "initial_agricultural_tech_level_in_use" "initial_healthcare_tech_level_in_use" "initial_housing_tech_level_in_use" "initial_transportation_tech_level_in_use" "initial_unaided_d_max_pop_density" "initial_unaided_not_dt_max_pop_density" "initial_unaided_t_max_pop_density" "initial_warfare_tech_level_in_use" "relevance_of_dist_based_on_transportation_tech_level" "initial_proportion_not_desert" "initial_pop_density_of_desert" "initial_pop_density_of_tundra" "initial_pop_density_ratio" "initial_transition_probability_to_desert"
 1 0 "Afrotropic" "Deserts & Xeric Shrublands" "Aldabra Island xeric scrub" 0.126710341015072 0.0256497364983143 0.00381482871869235 0.228069580194573 0.22121591571063 9.34871423966954 0.213750523128646 0.060993416566427 8.77072102617198 0.796054549237499 0.3 0.165705089524733 62.4162049928453 0.0022325486817456
 1 1 "Afrotropic" "Deserts & Xeric Shrublands" "Djibouti xeric shrublands" 0.34604 0.054555 0.064225 0.380625 0.0977975 9.597675 0.0573715 0.020765 -7.837 0.796054549237499 0.3 0.165705089524733 62.4162049928453 0.0022325486817456
 1 2 "Afrotropic" "Deserts & Xeric Shrublands" "Eritrean coastal desert" 0.13156 0.022495 0.010395 0.148425 0.0138715 2.716825 0.2614735 0.077325 -1.721 0.796054549237499 0.3 0.165705089524733 62.4162049928453 0.0022325486817456

src/sim_world_functions.py

@@ -6,6 +6,8 @@
 from scipy import stats
 
 def logistic_growth(previous_pop, r, carrying_cap):
+    if carrying_cap == 0:
+        carrying_cap = 0.1
     return round(previous_pop + r * previous_pop * (1 - previous_pop / carrying_cap))
 
 
@@ -126,3 +128,4 @@ def prior_biomes_before_desertification(n, rng:np.random.Generator):
     ).tolist()
 
     return past_biomes
+