This is an R Markdown Notebook which illustrates how to read a text file with geographic coordinates, convert it into a spatial feature object, and create a leaflet map.
This notebook is written to help Geomatica Basica students at Universidad Nacional de Colombia to get started with geospatial data in R.
# install libraries from console -NOT FROM HERE -
# if (!require('devtools')) install.packages('devtools')
# devtools::install_github('rstudio/leaflet')
# load libraries
library(sf)## Warning: replacing previous import 'vctrs::data_frame' by 'tibble::data_frame'
## when loading 'dplyr'## Linking to GEOS 3.7.2, GDAL 2.4.2, PROJ 5.2.0library(leaflet)cities <- read.table("../datos/cities.txt", sep=";", quote="", header=TRUE)# what is cities?
class(cities)## [1] "data.frame"# see the first records
head(cities)## X.id. X.cod. X.country. X.name. X.lat. X.lon. X.alt.
## 1 "1" 2338 "Colombi" "Bogota" 4.600000 -74.08334 2620
## 2 "2" 2339 "Colombi" "Cali" 3.437222 -76.52250 758
## 3 "3" 2340 "Colombi" "Medellin" 6.291389 -75.53611 2076
## 4 "4" 2341 "Colombi" "Barranquilla" 10.963889 -74.79639 33
## 5 "5" 2342 "Colombi" "Cartagena" 10.399722 -75.51444 36
## 6 "6" 2343 "Colombi" "Cucuta" 7.883333 -72.50528 314colnames(cities) <- c("id", "cod", "country", "name", "lat", "lon", "alt")# check column names
colnames(cities)## [1] "id" "cod" "country" "name" "lat" "lon" "alt"# load sf library
library(sf)
# convert dataframe object to simple feature object
# https://stackoverflow.com/questions/44214487/create-sf-object-from-two-column-matrix
m <- st_as_sf(cities,coords = c(6,5,7))
# This another way of executing the above line
# cities %>% sf::st_as_sf(coords = c(6,5,7)) -> m# what is m?
class(m)## [1] "sf" "data.frame"# get matrix of coordinates (lat, long, alt)
coords <- st_coordinates(m)# create vector of coordinates
# what are vectors in R
# https://datascienceplus.com/vectors-and-functions-in-r/#:~:text=A%20vector%20is%20the%20simplest,a%20vector%20of%20logical%20values.
lat = coords[, 2]
long = coords[,1]
alt = coords[,3]# leaflet review tutorial https://rstudio.github.io/leaflet/
# create leaflet map
mapa2 <- leaflet()
mapa2 <- addTiles(mapa2) # Add default OpenStreetMap map tiles
mapa2 <- addMarkers(mapa2, lng=long, lat=lat, popup=m$name)
# show map
mapa2You may explore other ways of visualization & mapping by reading the leaflet documentation here.
Another alternative for making maps in R can be seen here.
sessionInfo()## R version 3.6.3 (2020-02-29)
## Platform: x86_64-apple-darwin15.6.0 (64-bit)
## Running under: macOS Mojave 10.14.6
##
## Matrix products: default
## BLAS: /Library/Frameworks/R.framework/Versions/3.6/Resources/lib/libRblas.0.dylib
## LAPACK: /Library/Frameworks/R.framework/Versions/3.6/Resources/lib/libRlapack.dylib
##
## locale:
## [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
##
## attached base packages:
## [1] stats graphics grDevices utils datasets methods base
##
## other attached packages:
## [1] leaflet_2.0.3.9000 sf_0.9-5
##
## loaded via a namespace (and not attached):
## [1] Rcpp_1.0.5 knitr_1.29 magrittr_1.5 units_0.6-6
## [5] tidyselect_1.1.0 R6_2.4.1 rlang_0.4.7 stringr_1.4.0
## [9] dplyr_1.0.0 tools_3.6.3 grid_3.6.3 xfun_0.17
## [13] KernSmooth_2.23-17 e1071_1.7-3 DBI_1.1.0 crosstalk_1.1.0.1
## [17] ellipsis_0.3.1 htmltools_0.5.0 class_7.3-17 yaml_2.2.1
## [21] digest_0.6.25 tibble_3.0.3 lifecycle_0.2.0 crayon_1.3.4
## [25] purrr_0.3.4 htmlwidgets_1.5.1 vctrs_0.3.4 glue_1.4.2
## [29] evaluate_0.14 rmarkdown_2.3.5 stringi_1.5.3 pillar_1.4.6
## [33] compiler_3.6.3 generics_0.0.2 classInt_0.4-3 jsonlite_1.7.1
## [37] pkgconfig_2.0.3