rgeos::createPolygonsComment Is there some higher-level functionality in sf or terra that we can use for this

[rsbivand]

Thanks @rsbivand. With regard to rgeos::createPolygonsComment, it looks to me like we use this for sp Polygons objects whenever they're missing comment data indicating, for each hole, what non-hole they belong to.

createPolygonsComment attempts to create a valid comment for a Polygons object by assessing which polygons contain a given hole (using gContains). Ownership is assigned to the smallest polygon (by area) that contains the given hole.

rstudio/leaflet#833

[rsbivand]

From ?rgeos::createPolygonsComment:

library(sp)
p1 <- Polygon(cbind(x=c(0, 0, 10, 10, 0), y=c(0, 10, 10, 0, 0)), hole=FALSE) # I
p2 <- Polygon(cbind(x=c(3, 3, 7, 7, 3), y=c(3, 7, 7, 3, 3)), hole=TRUE) # H
p8 <- Polygon(cbind(x=c(1, 1, 2, 2, 1), y=c(1, 2, 2, 1, 1)), hole=TRUE) # H
p9 <- Polygon(cbind(x=c(1, 1, 2, 2, 1), y=c(5, 6, 6, 5, 5)), hole=TRUE) # H
p3 <- Polygon(cbind(x=c(20, 20, 30, 30, 20), y=c(20, 30, 30, 20, 20)), hole=FALSE) # I
p4 <- Polygon(cbind(x=c(21, 21, 29, 29, 21), y=c(21, 29, 29, 21, 21)), hole=TRUE) # H
p5 <- Polygon(cbind(x=c(22, 22, 28, 28, 22), y=c(22, 28, 28, 22, 22)), hole=FALSE) # I
p6 <- Polygon(cbind(x=c(23, 23, 27, 27, 23), y=c(23, 27, 27, 23, 23)), hole=TRUE) # H
p7 <- Polygon(cbind(x=c(13, 13, 17, 17, 13), y=c(13, 17, 17, 13, 13)), hole=FALSE) # I
p10 <- Polygon(cbind(x=c(24, 24, 26, 26, 24), y=c(24, 26, 26, 24, 24)), hole=FALSE) # I
p11 <- Polygon(cbind(x=c(24.25, 24.25, 25.75, 25.75, 24.25), y=c(24.25, 25.75, 25.75, 24.25, 24.25)), hole=TRUE) # H
p12 <- Polygon(cbind(x=c(24.5, 24.5, 25.5, 25.5, 24.5), y=c(24.5, 25.5, 25.5, 24.5, 24.5)), hole=FALSE) # I
p13 <- Polygon(cbind(x=c(24.75, 24.75, 25.25, 25.25, 24.75), y=c(24.75, 25.25, 25.25, 24.75, 24.75)), hole=TRUE) # H
	
lp <- list(p1, p2, p13, p7, p6, p5, p4, p3, p8, p11, p12, p9, p10)
#           1   2    3   4   5   6   7   8   9   10   11  12   13
#           0   1   11   0   6   0   8   0   1   13    0   1    0
#           I   H    H   I   H   I   H   I   H    H    I   H    I
spls <- SpatialPolygons(list(Polygons(lp, ID="1")))
comment(spls)
sapply(slot(spls, "polygons"), comment)
length(slot(slot(spls, "polygons")[[1]], "Polygons"))
spls1 <- spls
spls1 = rgeos::createSPComment(spls1)
comment(spls1)
sapply(slot(spls1, "polygons"), comment)
length(slot(slot(spls1, "polygons")[[1]], "Polygons"))
sapply(slot(as(sf::st_as_sfc(spls1), "Spatial"), "polygons"), comment)
length(slot(slot(as(sf::st_as_sfc(spls1), "Spatial"), "polygons")[[1]], "Polygons"))
spls_sfc <- sf::st_as_sfc(spls)
xx <- as(spls_sfc, "Spatial")
comment(xx)
sapply(slot(xx, "polygons"), comment)
length(slot(slot(xx, "polygons")[[1]], "Polygons"))
spls_sfc <- sf::st_as_sfc(spls, forceMulti=TRUE)
xx <- as(spls_sfc, "Spatial")
comment(xx)
sapply(slot(xx, "polygons"), comment)
length(slot(slot(xx, "polygons")[[1]], "Polygons"))

[rsbivand]

Need to check against GEOS version, it looks as though 3.9.3 is not sufficient. r-spatial/sf#2069 (comment)