generate_indices: Generate regional annual indices of abundance continent and...

In bbsBayes: Hierarchical Bayesian Analysis of North American BBS Data

Generate regional annual indices of abundance continent and strata and optionally for countries, states/provinces, or BCRs from analyses run on the stratifications that support these composite regions

Description

generate_indices creates a data frame of the annual indices of relative abundance by year. This data frame can then be used to plot population trajectories for the species, and to estimate trends.

Usage

generate_indices(
  jags_mod = NULL,
  jags_data = NULL,
  quantiles = c(0.025, 0.05, 0.25, 0.75, 0.95, 0.975),
  regions = c("stratum", "continental"),
  alternate_n = "n",
  startyear = NULL,
  drop_exclude = FALSE,
  max_backcast = NULL,
  alt_region_names = NULL
)

Arguments

jags_mod	JAGS list generated by run_model
jags_data	data object used in run_model
quantiles	vector of quantiles to be sampled from the posterior distribution Defaults to c(0.025,0.05,0.25,0.5,0.75,0.95,0.975)
regions	vector selecting regional compilation(s) to calculate. Default is "continental","stratum", options also include "national", "prov_state", "bcr", and "bcr_by_country" for the stratifications that include areas that align with those regions.
alternate_n	text string indicating the name of the alternative annual index parameter in a model, Default is "n", alternatives are "n2" which involves a different way of scaling the annual indices, "nsmooth" for the gam and gamye models which show only the smooth component of the trajectory, and "nslope" for the slope models which track only the linear slope component of the model
startyear	Optional first year for which to calculate the annual indices if a trajectory for only the more recent portion of the time series is desired. This is probably most relevant if max_backcast is set and so trajectories for different time-periods could include a different subset of strata (i.e., strata removed)
drop_exclude	logical indicating if the strata that exceed the max_backcast threshold should be excluded from the calculations, Default is FALSE (regions are flagged and listed but not dropped)
max_backcast	an optional integer indicating the maximum number of years to backcast the stratum-level estimates before the first year in which the species was observed on any route in that stratum. 5 is used in the CWS national estimates. If the observed data in a given stratum do not include at least one non-zero observation of the species between the first year of the BBS and startyear+max_backcast, the stratum is flagged within the relevant regional summary. Default value, NULL ignores any backcasting limit (i.e., generates annual indices for the entire time series, regardless of when the species was first observed)
alt_region_names	Optional dataframe indicating the strata to include in a custom spatial summary. Generate the basic dataframe structure with the extract_strata_areas function, then modify with an additional column indicating the strata to include in a custom spatial summary

Value

List of 6 objects

data_summary	dataframe with the following columns
Year	Year of particular index
Region	Region name
Region_alt	Long name for region
Region_type	Type of region including continental, national,Province_State,BCR, bcr_by_country, or stratum
Strata_included	Strata included in the annual index calculations
Strata_excluded	Strata potentially excluded from the annual index calculations because they have no observations of the species in the first part of the time series, see arguments max_backcast and startyear
Index	Strata-weighted count index
additional columns for each of the values in quantiles	quantiles of the posterior distribution
obs_mean	Mean of the observed annual counts of birds across all routes and all years. An alternative estimate of the average relative abundance of the species in the region and year. Differences between this and the annual indices are a function of the model. For composite regions (i.e., anything other than stratum-level estimates) this average count is calculated as an area-weighted average across all strata included
nrts	Number of BBS routes that contributed data for this species, region, and year
nrts_total	Number of BBS routes that contributed data for this species and region for all years in the selected time-series, i.e., all years since startyear
nnzero	Number of BBS routes on which this species was observed (i.e., count is > 0) in this region and year
backcast_flag	approximate annual average proportion of the covered species range that is free of extrapolated population trajectories. e.g., 1.0 = data cover full time-series, 0.75 = data cover 75 percent of time-series. Only calculated if max_backcast != NULL
samples	array of all posterior draws
area-weights	data frame of the strata names and area weights used to calculate the continental estimates
y_min	first year used in the summary, scale 1:length of time-series
y_max	last year used in the summary, scale 1:length of time-series
startyear	first year used in the summary, scale 1966:2018

Examples

# Toy example with Pacific Wren sample data
# First, stratify the sample data

strat_data <- stratify(by = "bbs_cws", sample_data = TRUE)

# Prepare the stratified data for use in a JAGS model.
jags_data <- prepare_jags_data(strat_data = strat_data,
                               species_to_run = "Pacific Wren",
                               model = "firstdiff",
                               min_year = 2009,
                               max_year = 2018)

# Now run a JAGS model.
jags_mod <- run_model(jags_data = jags_data,
                      n_adapt = 0,
                      n_burnin = 0,
                      n_iter = 10,
                      n_thin = 1)

# Generate the continental and stratum indices
indices <- generate_indices(jags_mod = jags_mod,
                            jags_data = jags_data)

# Generate only national indices
indices_nat <- generate_indices(jags_mod = jags_mod,
                                jags_data = jags_data,
                                regions = c("national"))

bbsBayes documentation built on March 7, 2023, 6:33 p.m.