An R package to extract NOAA night lights data for regions within shapefiles
(a SpatialPolygons or SpatialPolygonsDataFrame). The night lights data can be downloaded from
here or using the
function downloadNightLights() in the package. Alternatively, a download
script is provided to download and extract all the data (see below).
if (!require(devtools)) install.packages("devtools")
devtools::install_github("walshc/nightlights")require(nightlights)
# Download, extract and load and example shapefile to work with (US counties):
download.file("ftp://ftp2.census.gov/geo/tiger/TIGER2015/COUSUB/tl_2015_25_cousub.zip",
destfile = "tl_2015_25_cousub.zip")
unzip("tl_2015_25_cousub.zip")
shp <- rgdal::readOGR(".", "tl_2015_25_cousub")
# Download and extract some night lights data to a directory "night-lights":
downloadNightLights(years = 1999:2000, directory = "night-lights")
# By default, the function gets the sum of night lights within the regions:
nl.sums <- extractNightLights(directory = "night-lights", shp)
# You can specificy other statistics to get, e.g. the mean & standard deviation:
nl.mean.sd <- extractNightLights(directory = "night-lights", shp,
stats = c("mean", "sd"))If the night lights directory contains the data for years 1999 and 2000 and stats = "sum":
GEOID NAME night.lights.1999.sum night.lights.2000.sum
0 2502328285 Hanover 3613.0 3587.0
1 2502338855 Marshfield 5726.5 5253.5
2 2502350145 Norwell 4494.0 4268.5
3 2502372985 Wareham 5625.5 5338.0
4 2500300975 Alford 324.5 409.0
5 2500334970 Lenox 2339.5 2661.0
Instead of downloading all the data using the downloadNightLights() function, I also provide a script (download-and-extract-lights-data.sh) which should work in the terminal on OS X and Linux. The script will ask which directory you want to save the night lights data to. Keep in mind the full data set is very large so you will need about 50GB of space to do this. You can choose to save it to an external drive if you wish. Paste the following command into the terminal to get it started:
curl https://raw.githubusercontent.com/walshc/nightlights/master/download-and-extract-lights-data.sh | bash
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