dggridR: Discrete Global Grids for R

Spatial Analysis Done Right

You want to do spatial statistics, and it’s going to involve binning.

Binning with a rectangular grid introduces messy distortions. At the macro-scale using a rectangular grid does things like making Greenland bigger than the United States and Antarctica the largest continent.

But this kind of distortion is present no matter what the resolution is; in fact, it shows up whenever you project a sphere onto a plane.

What you want are bins of equal size, regardless of where they are on the globe, regardless of their resolution.

dggridR solves this problem.

dggridR builds discrete global grids which partition the surface of the Earth into hexagonal, triangular, or diamond cells, all of which have the same size. (There are some minor caveats which are detailed in the vignettes.)

(Naturally, you can use much smaller cells than those shown in the image above.)

This package includes everything you need to make spatial binning great again.

Many details and examples are included in the vignette.

Installation

dggridR is available from CRAN via:

install.packages('dggridR')

If you want your code to be as up-to-date as possible, you can install it using:

library(devtools) #Use `install.packages('devtools')` if need be
devtools::install_github("r-barnes/dggridR", vignette=TRUE)

Show me some code

Okay.

Your analysis could be as easy as this:

library(dggridR)
library(dplyr)

#Construct a global grid with cells approximately 1000 miles across
dggs          <- dgconstruct(spacing=1000, metric=FALSE, resround='down')

#Load included test data set
data(dgquakes)

#Get the corresponding grid cells for each earthquake epicenter (lat-long pair)
dgquakes$cell <- dgGEO_to_SEQNUM(dggs, dgquakes$lon, dgquakes$lat)$seqnum

#Get the number of earthquakes in each equally-sized cell
quakecounts   <- dgquakes %>% group_by(cell) %>% summarise(count=n())

Show me more examples!

In R, typing

vignette('dggridR')

will bring up many examples.

But I want higher resolution grids than that

Many different grid resolutions are available for many different grids. The following chart shows the number of cells, their area, and statistics regarding the spacing of their center nodes for the ISEA3H grid type.

Res	Number of Cells	Cell Area (km^2)	Min	Max	Mean	Std
1	32	17,002,187.39080	4,156.18000	4,649.10000	4,320.49000	233.01400
2	92	5,667,395.79693	2,324.81000	2,692.72000	2,539.69000	139.33400
3	272	1,889,131.93231	1,363.56000	1,652.27000	1,480.02000	89.39030
4	812	629,710.64410	756.96100	914.27200	855.41900	52.14810
5	2,432	209,903.54803	453.74800	559.23900	494.95900	29.81910
6	7,292	69,967.84934	248.80400	310.69300	285.65200	17.84470
7	21,872	23,322.61645	151.22100	187.55000	165.05800	9.98178
8	65,612	7,774.20548	82.31100	104.47000	95.26360	6.00035
9	196,832	2,591.40183	50.40600	63.00970	55.02260	3.33072
10	590,492	863.80061	27.33230	35.01970	31.75960	2.00618
11	1,771,472	287.93354	16.80190	21.09020	18.34100	1.11045
12	5,314,412	95.97785	9.09368	11.70610	10.58710	0.66942
13	15,943,232	31.99262	5.60065	7.04462	6.11367	0.37016
14	47,829,692	10.66421	3.02847	3.90742	3.52911	0.22322
15	143,489,072	3.55473	1.86688	2.35058	2.03789	0.12339
16	430,467,212	1.18491	1.00904	1.30335	1.17638	0.07442
17	1,291,401,632	0.39497	0.62229	0.78391	0.67930	0.04113
18	3,874,204,892	0.13166	0.33628	0.43459	0.39213	0.02481
19	11,622,614,672	0.04389	0.20743	0.26137	0.22643	0.01371
20	34,867,844,012	0.01463	0.11208	0.14489	0.13071	0.00827

Credits

The code in the ‘src’ directory is based off of DGGRIDv6.2b by Kevin Sahr.

However, Richard Barnes has made some significant alterations. These include:

Replacement of gpclib with clipper, thus making DGGRID into FLOSS software available for both commercial and non-commercial use without restriction
Restructuring and simplifying all of the makefiles to enable compilation in R
Direct inclusion of the shapelib library
Addition of the SEQTOPOLY option under the GENERATE_GRID faculty
Alterations that enable the code to be compiled under GCC6
Alterations that make the code ISO C conformant
Alterations to resolve -pedantic and -Wall warnings

The package relies on several libraries, as noted in the Licensing section below.

Licensing

This package uses the following libraries:

clipper: The clipper library has been released under the Boostv1 license by Angus Johnson
dggrid: Kevin Sahr has released dggrid as a “public domain software program”
proj4lib: Gerald Evenden has released this code into the public domain. More recent versions of the library, not used here, are under an MIT-style license.
shapelib: Frank Warmerdam has released shapelib under an MIT-style license. There is also an LGPL licensing option which I have chosen not to use.

This package, and all code and documentation not otherwise mentioned above (essentially anything outside the src/ directory of this package) are released under the MIT (Expat) license, as stated in the LICENSE file. The LICENCE file exists for use with CRAN.

Disclaimer

This package should operate in the manner described here, in the package’s main documentation, and in Kevin Sahr’s dggrid documentation. Unfortunately, none of us are paid enough to make absolutely, doggone certain that that’s the case. That said, if you find bugs or are seeking enhancements, we want to hear about them.

Citing this Package

Please cite this package as:

Richard Barnes and Kevin Sahr (2017). dggridR: Discrete Global Grids for R. R package version 2.0.4. “https://github.com/r-barnes/dggridR/” doi:10.5281/zenodo.1322866