01_georeference.qmd

---
title: Latitude and Longitude Coordinates
---

Use the [`mapview` package](https://r-spatial.github.io/mapview/index.html) to make interactive maps. In this example, georeference Starbucks coffee shop locations in North Carolina (2012). [^1]

[^1]: [5 Visualizations in 5 Minutes](http://www.computerworld.com/article/2893271/business-intelligence/5-data-visualizations-in-5-minutes-each-in-5-lines-or-less-of-r.html). ComputerWorld.com by Sharon Machlis

## Load Libraries

```{r}
#| label: libraries
#| message: false
#| warning: false

library(tidyverse)
library(sf)
library(mapview)
```

## Load Data

2012 Starbucks locations ([data source](https://github.com/libjohn/mapping-with-R/blob/master/data/All_Starbucks_Locations_in_the_US_-_Map.csv))

```{r}
#| label: load-data
#| message: false
#| warning: false

starbucks <- read_csv("https://raw.githubusercontent.com/libjohn/mapping-with-R/master/data/All_Starbucks_Locations_in_the_US_-_Map.csv", show_col_types = FALSE)
```

### Subset Data to North Carolina

```{r}
#| label: filter-dataset
#| message: false
#| warning: false

starbucksNC <- starbucks  %>% 
  filter(State == "NC")

starbucksNC %>% 
  glimpse()
```

## Make the Map

In this example, plot latitude (y coordinates) and longitude (x coordinates). Then set the map projection[^2] to a common projection standard such as *WGS84* via the argument `crs = 4326`.)

[^2]: [Projection / CRS](https://guides.library.duke.edu/r-geospatial/CRS)

```{r}
mapview(starbucksNC, xcol = "Longitude", ycol = "Latitude", crs = 4269, grid = FALSE)
```

## Alternative: Transform data to Spatial object

Another way to plot the x & y coordinates is by transforming the starbucksNC tibble (i.e. the starbucksNC data frame) into a spacial data frame via the simple features function, `st_as_sf()`. Again, set the [map projection](https://en.wikipedia.org/wiki/Map_projection) to a common standard such as *WGS84* via the `crs=` argument.

```{r}
sbux_sf <- st_as_sf(starbucksNC, coords = c("Longitude", "Latitude"),  crs = 4326)
```

### Now Map the sf object.

Below, you can plot the latitude and longitude coordinate, and set the `map.types` argument.

This time with a different basemap...

```{r}
# mapview(sbux_sf)
mapview(sbux_sf, map.types = "CartoDB.DarkMatter") 
```