inlet_helpers: Convenience functions to create an inlet zoom map

In d-qn/taMap: Convenience functions for geomapping Swiss data

Convenience functions to create an inlet zoom map

Description

The steps are: 1. Create a sf ojbect with shifted geospatial coordinates and/or scaled-up/down 2. Create a sf ojbect that encirle 1, totally unnecessary but aesthically pleasing. 3. Create a sf ojbect that encircle the original region that was shifted & scaled-up 4. Create a sf ojbect that connects both circles to convey it a zoomed inlet map encircle_coord finds the centre and radius to completely encompass the provided geospatial object encircle_geo takes a named list with centre and radius and return a simple feature object of the circle

Usage

shiftScale_geo(geo, shiftM = c(-9000, 150000), scaleF = 3)

encircle_coord(geo)

encircle_geo(centreRadius)

cone_geo(centreRadius_ori, centreRadius_inlet)

Arguments

geo	a simple feature data.frame
shiftM	a numeric of length 2, the distances in meters to shift in longitude and latitude respectively
scaleF	a numeric of length 1, the scaling factor
centreRadius, centreRadius_ori, centreRadius_inlet	a named list with centre (a sfc_POINT) and radius

Value

shiftScale_geo a simple feature data.frame

encircle_coord a named list with a simple feature point (centre) and the radius in meters

encircle_geo a simple feature object

cone_geo a simple feature object

Examples

## Not run: 
require(sf)
require(tidyverse)

shp_ch_paths_2018 <- shp_path(2018)
# loop and load the geo data in a named list
shp_ch_geodata <- shp_ch_paths_2018 %>% map(function(x) {
  layerName <- st_layers(x)
  st_read(x, layer = layerName$name) %>% 
  select(ends_with("NR"), ends_with("NAME"))
})

# shift and scale up canton Geneva for the inlet map
geo_subset <- shp_ch_geodata$municipalities %>% filter(KTNR == 25)
inlet_geo <- shiftScale_geo(geo = geo_subset, scaleF = 4.4)

# Create circles sf to encompass the inlet map and its original location
geo_subset_coord <- encircle_coord(geo_subset)
inlet_coord <- encircle_coord(inlet_geo)

cone_sfc <- cone_geo(geo_subset_coord, inlet_coord)
circle_zoom_sfc <- encircle_geo(geo_subset_coord)
circle_inlet_sfc <- encircle_geo(inlet_coord)

# plot
gp <- ggplot() +
  geom_sf(data = cone_sfc, fill = "lightgrey", lwd = 0, alpha = 0.2) +  
  geom_sf(data = circle_zoom_sfc, fill = "lightgrey", lwd = 0, alpha = 0.5) +
  geom_sf(data = circle_inlet_sfc, fill = "lightgrey", lwd = 0, alpha = 0.5) +
  geom_sf(data = shp_ch_geodata$municipalities, aes(fill = GMDNR), 
    lwd = 0.05, colour = "#0d0d0d") +
  geom_sf(data = inlet_geo, aes(fill = GMDNR), lwd = 0.1, colour = "#0d0d0d") +
  geom_sf(data = shp_ch_geodata$cantons, lwd = 0.15, colour = "#333333", fill = NA) +
  geom_sf(data = shp_ch_geodata$country, lwd = 0.25, colour = "#000d1a", fill = NA) +
  geom_sf(data = shp_ch_geodata$lakes, lwd = 0, fill = "#0066cc")

  gp + 
    theme_map() +
    scale_fill_viridis_c()  +
    coord_sf(datum = NA, expand = F)

## End(Not run)

d-qn/taMap documentation built on Nov. 23, 2024, 7:42 a.m.