HatchedPolygons

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HatchedPolygons

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Create a hatched area for SpatialPolygons in R

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# HatchedPolygons

[![DOI](https://zenodo.org/badge/90766217.svg)](https://zenodo.org/badge/latestdoi/90766217)
[![R-CMD-check](https://github.com/statnmap/HatchedPolygons/actions/workflows/R-CMD-check.yaml/badge.svg)](https://github.com/statnmap/HatchedPolygons/actions/workflows/R-CMD-check.yaml)

This R package creates a area filled by SpatialLines to allow for
hatched areas in SpatialPolygons.  
This may be particularly useful when SpatialPolygons show holes but also
for drawing hatched areas in leaflet Polygons.

To install it:

devtools::install_github("statnmap/HatchedPolygons")

## Create a hatched area for SpatialPolygons in R

### With {sp}

``` r
library(sp)
library(sf)
library(HatchedPolygons)
library(ggplot2)

# Create two polygons: second would be a hole inside the first
xy <- cbind(
  x = c(13.4, 13.4, 13.6, 13.6, 13.4),
  y = c(48.9, 49, 49, 48.9, 48.9)
)
hole.xy <- cbind(
  x = c(13.5, 13.5, 13.45, 13.45, 13.5),
  y = c(48.98, 48.92, 48.92, 48.98, 48.98)
)

# Create SpatialPolygon
xy.sp <- SpatialPolygonsDataFrame(
  SpatialPolygons(list(
    Polygons(list(
      Polygon(xy),
      Polygon(hole.xy, hole = TRUE)
    ), "1"),
    Polygons(list(
      Polygon(hole.xy + 0.2, hole = TRUE),
      Polygon(xy + 0.2),
      Polygon(xy + 0.35)
    ), "2")
  )),
  data = data.frame(id = as.character(c(1, 2)))
)

# Allows for different hatch densities and directions for each polygon
xy.sp.hatch <- hatched.SpatialPolygons(xy.sp, density = c(40, 60), angle = c(45, 135))

# Draw again polygons with holes
par(bg = "lightblue", mar = c(2, 2, 0.5, 0.5))
plot(xy.sp, col = c("blue", "red"))
plot(xy.sp.hatch,
  col = c("cyan", "grey90")[as.numeric(xy.sp.hatch$ID)],
  lwd = 3, add = TRUE
)
```

### With {sf}

*Note that the current implementation transforms sf object as sp, then
back to sf*

``` r
# Also with {sf}
xy.sf <- sf::st_as_sf(xy.sp) # simulate st_read()
xy.sf.hatch <- hatched.SpatialPolygons(xy.sf, density = c(40, 60), angle = c(45, 135))

# Plot with ggplot2
ggplot(xy.sf) +
  geom_sf(aes(colour = id),
    fill = "transparent", size = 1.5
  ) +
  geom_sf(
    data = xy.sf.hatch,
    aes(colour = ID),
    size = 1
  ) +
  guides(col = FALSE)
#> Warning: The `<scale>` argument of `guides()` cannot be `FALSE`. Use "none" instead as
#> of ggplot2 3.3.4.
#> This warning is displayed once every 8 hours.
#> Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
#> generated.
```

See documentation on the pkgdown website for details :
<https://statnmap.github.io/HatchedPolygons/>

![Hatched Polygons with Leaflet](https://raw.githubusercontent.com/statnmap/HatchedPolygons/master/reference/figures/Leaflet_Snapshot.jpg)

*Description of this function can be found on
[statnmap.com](https://statnmap.com/2017-05-23-how-to-fill-a-hatched-area-polygon-with-holes-in-leaflet-with-r)*  
*More on my website: [Freelance - Courses and consulting in modeling
with R](https://statnmap.com/)*

There is also a vignette:

vignette("leaflet_shading_polygon", package = "HatchedPolygons")

Citation:  
Sébastien Rochette. (2017, August 18). Hatched area in polygons with R -
v0.1.0. Zenodo. <http://doi.org/10.5281/zenodo.845493>

HatchedPolygons

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