oceans-diff.R

``` r
library(tidyverse)
library(raster)
library(sf)
#> Linking to GEOS 3.6.1, GDAL 2.2.3, PROJ 4.9.3

oceans <- 
  rnaturalearth::ne_download(scale = 10, 
                             category = "physical", 
                             type = "ocean",
                             returnclass = "sf")
#> OGR data source with driver: ESRI Shapefile 
#> Source: "C:\Users\Cedric\AppData\Local\Temp\RtmpKQR6db", layer: "ne_10m_ocean"
#> with 1 features
#> It has 3 fields

ggplot(oceans) + geom_sf(fill = "dodgerblue")
```

![](https://i.imgur.com/wjDgmYB.png)

``` r

bbox <- as(extent(4, 16, 39, 51), 'SpatialPolygons') 
crs(bbox) <- crs(oceans)

oceans_med <- oceans %>% 
  st_crop(., bbox)
#> although coordinates are longitude/latitude, st_intersection assumes that they are planar
#> Warning: attribute variables are assumed to be spatially constant throughout all
#> geometries

ggplot(oceans_med) + geom_sf(fill = "dodgerblue")
```

![](https://i.imgur.com/UqjkqtG.png)

``` r


oceans_fix <- st_difference(oceans_med, st_as_sfc(st_bbox(oceans_med)))
#> although coordinates are longitude/latitude, st_difference assumes that they are planar
#> Warning: attribute variables are assumed to be spatially constant throughout all
#> geometries

ggplot(oceans_fix) + geom_sf(fill = "dodgerblue")
```

![](https://i.imgur.com/zJsJB75.png)

<sup>Created on 2020-04-07 by the [reprex package](https://reprex.tidyverse.org) (v0.3.0)</sup>