Paanwaris Paansri and Luis E. Escobar
Ecological Motivation
The bean package provides a tool to address a fundamental challenge in species distribution modeling (SDM, or ecological niche modeling, ENM): sampling bias. Occurrence records for species are rarely collected through a systematic, stratified process. Instead, they often cluster in easily accessible areas (like roads and cities) or in well-studied research sites. This spatial bias can translate into an environmental bias, where the model incorrectly learns that the species is associated with the environmental conditions of those heavily sampled areas, rather than its true ecological requirements.
bean tackles this problem by thinning occurrence data in environmental space. The goal is to create a more uniform distribution of points across the species’ observed environmental niche, reducing the influence of densely clustered records. This allows for the construction of a more accurate fundamental niche volume, which can then be projected into geographic space to create a less biased prediction of area with environmental suitability.
The name bean reflects the core principle of the method: ensuring that each “pod” (a grid cell in environmental space) contains only a specified number of “beans” (occurrence points).
Package Description
bean operates by shifting the focus from geographic space to environmental space:
Environmental Gridding: Divides the environmental hypercube into “pods”.
Objective Thinning: Reduces clusters to a specified density per pod.
Niche Delineation: Fits ellipsoids to thinned data to define the fundamental niche.
Projection: Maps the corrected niche back into geographic space for less biased predictions.
Installing the Package
The development version of bean can be installed from GitHub:
# Install devtools if needed
if (!require("devtools")) install.packages("devtools")
# Install bean
devtools::install_github("paanwaris/bean")To load the package:
The bean Protocol: Step-by-Step
A typical bean workflow consists of these key steps:
1. Data Preparation
The prepare_bean() function cleans raw occurrence data by removing missing coordinates and extracting environmental values from raster layers. This ensures all subsequent analyses use a clean, scaled dataset.
See the Preparing bean vignette.
2. Objective Grid Resolution
Instead of arbitrary thinning, find_env_resolution() uses a geometric “elbow” method based on nearest-neighbor distances in E-space. This identifies the exact distance where dense artificial clustering transitions into natural data spacing.
See the Finding the environmental resolution vignette.
3. Apply Thinning
bean offers two core thinning methods:
Stochastic (
thin_env_nd): Randomly samples one “bean” from each occupied “pod”.Deterministic (
thin_env_center): Generates a new point at the exact center of every occupied grid cell.
See the Apply thinning vignette.
4. Niche Delineation
The fit_ellipsoid() function formalizes the environmental niche by fitting a bivariate or multivariate ellipse around the thinned points.
See the Niche delineation vignette.
5. Prediction and Mapping
Using the learned niche, predict() projects the results back to geographic space. This step emphasizes the ellipsoid-based approach is used to calculate suitability scores from the delineated niche boundaries.
See the Prediction and mapping vignette.
Checking the Vignettes
For full demonstrations of the protocol, check the package vignettes:
# Data Preparation & Visualization
vignette("data-preparation")
#> Warning: vignette 'data-preparation' not found
# Objective Thinning in Environmental Space
vignette("environmental-thinning")
#> Warning: vignette 'environmental-thinning' not found
# Niche Delineation & Suitability Mapping
vignette("niche-modeling")
#> Warning: vignette 'niche-modeling' not foundThe End ❤️