CODEWITHSUNDEEP
rr-sf
TreausreDragon
TreausreDragon

Reputation: 61

How can I convert a list of coordinates into an SF Multipolygon file?

newdata
             V1        V2
1    -2.8701091 8273.6321
2     4.8298909 8273.6321
3    21.3298909 8279.1321
4    25.7298909 8281.3321
5    32.3298909 8285.7321
6    46.6298909 8298.9321

V1 is x and V2 is y and I want to know if there was a way to convert this into an sf multipolygon file. Newdata has 941 polygons and each polygon has roughly 19 rows each. Thank you! Here is a reproducible dataset for the first two polygons:

> dput(head(newdata, 38))
structure(list(.id = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L), V1 = c(-2.8701090548579, 
4.8298909451421, 21.3298909451421, 25.7298909451421, 32.3298909451421, 
46.6298909451421, 47.7298909451421, 55.4298909451421, 64.2298909451421, 
67.5298909451421, 67.5298909451421, 65.3298909451421, 54.3298909451421, 
52.1298909451421, 48.8298909451421, 46.6298909451421, 34.5298909451421, 
-2.8701090548579, -2.8701090548579, -1.79600509987251, 9.2039949001275, 
20.2039949001275, 25.7039949001275, 37.8039949001275, 41.1039949001275, 
44.4039949001275, 44.4039949001275, 38.9039949001275, 35.6039949001275, 
33.4039949001275, 32.3039949001275, 29.0039949001275, 20.2039949001275, 
16.9039949001275, 11.4039949001275, 0.403994900127497, -1.79600509987251, 
-1.79600509987251), V2 = c(8273.63213813615, 8273.63213813615, 
8279.13213813615, 8281.33213813615, 8285.73213813615, 8298.93213813615, 
8300.03213813615, 8313.23213813615, 8333.03213813615, 8356.13213813615, 
8381.43213813615, 8385.83213813615, 8401.23213813615, 8403.43213813615, 
8405.63213813615, 8406.73213813615, 8406.73213813615, 8395.73213813615, 
8273.63213813615, 7198.72511687208, 7198.72511687208, 7199.82511687208, 
7202.02511687208, 7213.02511687208, 7216.32511687208, 7222.92511687208, 
7236.12511687208, 7251.52511687208, 7258.12511687208, 7261.42511687208, 
7262.52511687208, 7264.72511687208, 7269.12511687208, 7270.22511687208, 
7271.32511687208, 7271.32511687208, 7270.22511687208, 7198.72511687208
)), row.names = c(NA, 38L), class = "data.frame")

Upvotes: 2

Views: 2088

Answers (1)

SymbolixAU
SymbolixAU

Reputation: 26248

Converting R objects to {sf} objects is exactly the use-case for {sfheaders}

If your .id column specifies each POLYGON within a single MULTIPOLYGON, then use the argument polygon_id = ".id"

library(sf)
library(sfheaders)

sfheaders::sf_multipolygon(
  obj = newData
  , polygon_id = ".id"
  , x = "V1"
  , y = "V2"
)

Simple feature collection with 1 feature and 1 field
Geometry type: MULTIPOLYGON
Dimension:     XY
Bounding box:  xmin: -2.870109 ymin: 7198.725 xmax: 67.52989 ymax: 8406.732
CRS:           NA
id                       geometry
1  1 MULTIPOLYGON (((-2.870109 8...

If your .id column represents each MULTIPOLYGON, use the argument multipolygon_id = ".id"

sfheaders::sf_multipolygon(
 obj = newData
 , multipolygon_id = ".id"
 , x = "V1"
 , y = "V2"
)

Simple feature collection with 2 features and 1 field
Geometry type: MULTIPOLYGON
Dimension:     XY
Bounding box:  xmin: -2.870109 ymin: 7198.725 xmax: 67.52989 ymax: 8406.732
CRS:           NA
.id                       geometry
1   1 MULTIPOLYGON (((-2.870109 8...
2   2 MULTIPOLYGON (((-1.796005 7...

Upvotes: 3

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