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)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
sfcrs 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.
Value
Vetorized trends data as an sf object.
Examples
if (FALSE) { # \dontrun{
# 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")
} # }