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Calculate Grid Cell Coverage by International State System Boundaries (cShapes 2.0)

Source: R/data_cshapes.R
cshapes_cover_share.Rd

Computes the proportion of each PRIO-GRID cell that intersects with country boundaries from the CShapes 2.0 dataset at a specified date. The function performs spatial overlay analysis to determine how much of each grid cell falls within internationally recognized state boundaries.

Usage

cshapes_cover_share(measurement_date, cshp = read_cshapes())

Arguments

measurement_date

A single Date object specifying the date for which to calculate boundary coverage. Must be within the temporal range of the CShapes dataset (1886 onwards).

cshp

An sf object containing CShapes 2.0 boundary data with properly formatted date intervals. Defaults to read_cshapes() if not provided.

Details

This function uses CShapes 2.0 historical boundary data to calculate the proportion of each PRIO-GRID cell covered by countries that were part of the international state system at the measurement date. The function:

  • Filters CShapes data to boundaries valid at the measurement date

  • Performs exact area-weighted extraction using the exactextractr package

  • Returns proportional coverage values (0-1) for each grid cell

  • Masks out non-land areas from the final result

The coverage values represent the fraction of each PRIO-GRID cell area that falls within internationally recognized state boundaries.

References

Schvitz G, Girardin L, Rüegger S, Weidmann NB, Cederman L, Gleditsch KS (2022). “Mapping the International System, 1886-2019: The CShapes 2.0 Dataset.” Journal of Conflict Resolution, 66(1), 144–161. ISSN 0022-0027, doi:10.1177/00220027211013563 , 2024-11-22.

See also

read_cshapes for loading CShapes boundary data, prio_blank_grid for PRIO-GRID structure, exact_extract for area-weighted extraction

Examples

if (FALSE) { # \dontrun{
# Calculate state system coverage for 2010
coverage_2010 <- cshapes_cover_share(as.Date("2010-01-01"))

# View the result
print(coverage_2010)

# Plot the coverage
terra::plot(coverage_2010,
            main = "cShapes coverage 2010",
            col = terrain.colors(100))

# Calculate coverage for different time periods
coverage_1950 <- cshapes_cover_share(as.Date("1950-01-01"))
coverage_2000 <- cshapes_cover_share(as.Date("2000-01-01"))

# Compare coverage over time
coverage_change <- coverage_2000 - coverage_1950
terra::plot(coverage_change,
            main = "Change in cShapes coverage 1950-2000")

} # }