Improve description of topological relations

[Robinlovelace]

Currently in the book the section on topological relations starts as follows:

Link: https://geocompr.robinlovelace.net/spatial-operations.html#topological-relations

We can do better than that!

I'm looking at early papers on the subject and came across these illustrations:

Source: https://en.wikipedia.org/wiki/DE-9IM#cite_note-sdh1990-4

[Robinlovelace]

See below a start on the figure. Any feedback welcome. Reproducible code creating that image in subsequent commit.

[Robinlovelace]

More progress on this, reproducible example:

source("https://github.com/Robinlovelace/geocompr/raw/c4-v2-updates-rl/code/de_9im.R")
p1 = st_sfc(st_polygon(list(rbind(c(0, 0), c(1, 0), c(1, 1), c(0, 0)))))
p2 = st_sfc(st_polygon(list(rbind(c(0, 0), c(0, 1), c(1, 1), c(0, 0)))))
p3 = st_sfc(st_polygon(list(rbind(c(0.7, 0.3), c(0.7, 0.95), c(0.9, 0.95), c(0.7, 0.3)))))
p4 = st_sfc(st_polygon(list(rbind(c(0.6, 0.1), c(0.7, 0.5), c(0.9, 0.5), c(0.6, 0.1)))))
p5 = st_sfc(st_polygon(list(rbind(c(0, 0.2), c(0, 1), c(0.9, 1), c(0, 0.2)))))
de_9im(p1, p2)
de_9im(p1, p3)
de_9im(p1, p4)
de_9im(p4, p1)
de_9im(p1, p5)

source("https://github.com/Robinlovelace/geocompr/raw/c4-v2-updates-rl/code/de_9im.R")
library(sf)
#> Linking to GEOS 3.9.1, GDAL 3.3.2, PROJ 7.2.1
p1 = st_sfc(st_polygon(list(rbind(c(0, 0), c(1, 0), c(1, 1), c(0, 0)))))
p2 = st_sfc(st_polygon(list(rbind(c(0, 0), c(0, 1), c(1, 1), c(0, 0)))))
p3 = st_sfc(st_polygon(list(rbind(c(0.7, 0.3), c(0.7, 0.95), c(0.9, 0.95), c(0.7, 0.3)))))
p4 = st_sfc(st_polygon(list(rbind(c(0.6, 0.1), c(0.7, 0.5), c(0.9, 0.5), c(0.6, 0.1)))))
p5 = st_sfc(st_polygon(list(rbind(c(0, 0.2), c(0, 1), c(0.9, 1), c(0, 0.2)))))
de_9im(p1, p2)
#> Object x has the following spatial relations to y: st_intersects
#> st_touches

de_9im(p1, p3)
#> Object x has the following spatial relations to y: st_intersects
#> st_overlaps

de_9im(p1, p4)
#> Object x has the following spatial relations to y: st_intersects
#> st_contains
#> st_contains_properly
#> st_covers

de_9im(p4, p1)
#> Object x has the following spatial relations to y: st_intersects
#> st_within
#> st_covered_by

de_9im(p1, p5)
#> Object x has the following spatial relations to y: st_disjoint

^{Created on 2021-11-15 by the reprex package (v2.0.1)}

[Robinlovelace]

After the commit above we have the following 4.2, an improvement on the previous one but we can make it better. Thinking it would benefit from more geometries, maybe links on the bottom row?

[Robinlovelace]

Latest text output:

[Robinlovelace]

This is now MVP, we can tweak after but for this figure this is an improvement. Now I just need to complete my review of c4!