ebirdst (version 3.2023.1)

vectorize_trends: Convert Trends Data Products to points or circles

Description

The eBird trends data are stored in a tabular format, where each row gives the trend estimate for a single cell in a 27 km x 27 km equal area grid. For many applications, an explicitly spatial format is more useful. This function uses the cell center coordinates to convert the tabular trend estimates to points or circles in sf format. Trends can be converted to points or to circles with areas roughly proportional to the relative abundance within that 27 km grid cell. These abundance-scaled circles are what is used to produce the trends maps on the eBird Status and Trends website.

Usage

vectorize_trends(trends, output = c("circles", "points"), crs = 4326)

Value

Vetorized trends data as an sf object.

Arguments

trends

data frame; trends data for a single species as returned by load_trends().

output

character; "points" outputs spatial points while "circles" outputs circles with areas roughly proportional to the relative abundance within that 27 km grid cell.

crs

character or sf crs object; coordinate reference system to output the results in. For points, unprojected latitude-longitude coordinates (the default) are most typical, while for circles use whatever equal area CRS you intend to use when mapping the data otherwise the "circles" will appear skewed.

Examples

if (FALSE) {
# download example trends data if it hasn't already been downloaded
ebirdst_download_trends("yebsap-example")

# load trends
trends <- load_trends("yebsap-example")

# vectorize as points
vectorize_trends(trends, "points")
# vectorize as circles
vectorize_trends(trends, "circles", crs = "+proj=eqearth")
}