how to create several polygons from a list of vertices

Thanks Lulla,

Nice solution. I could also export it as a shapefile after transforming it
to a spatial polygon dataframe.

The problem is that I could not "individualize" the squares in a multipart
layer. They all have the same ID. I tried to change this without success:
"Single ID required".

The attribute table of the shapefile should have 6 lines in my example and
not only one.

Any other option?

Thanks again,

Antonio Olinto


Em ter, 14 de ago de 2018 ?s 18:10, Vijay Lulla <vijaylulla at gmail.com>
escreveu:

Maybe something like this?

poly <- SpatialPolygons(list(Polygons(tapply(seq_len(nrow(vertices)),
                                             vertices$cod,
                                             function(x)
Polygon(vertices[x,1:2])), ID="1")),
                        proj4string=CRS("+proj=longlat +ellps=WGS84
+datum=WGS84 +no_defs"))


On Tue, Aug 14, 2018 at 4:17 PM Antonio Silva <aolinto.lst at gmail.com>
wrote:

Hi,

I have a data.frame with the vertices (lon / lat) and codes from several
squares (more than 500 in the real dataset).
I want to create an object with these polygons (squares) and after this
export it as a shapefile.
With the script below I can draw one square.
library(sp)
P1 = Polygon(vertices[1:4,1:2])
Ps1 = SpatialPolygons(list(Polygons(list(P1), ID = "1")),
proj4string=CRS("+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs"))
plot(Ps1, axes = TRUE)

Now I'm trying to create one object with all squares at once.
Is it possible?

Thanks a lot,

Ant?nio Olinto

sample data:vertices
   lon lat cod
1  -33 -23   1
2  -32 -23   1
3  -32 -22   1
4  -33 -22   1
5  -32 -23   2
6  -31 -23   2
7  -31 -22   2
8  -32 -22   2
9  -31 -23   3
10 -30 -23   3
11 -30 -22   3
12 -31 -22   3
13 -33 -22   4
14 -32 -22   4
15 -32 -21   4
16 -33 -21   4
17 -32 -22   5
18 -31 -22   5
19 -31 -21   5
20 -32 -21   5
21 -31 -22   6
22 -30 -22   6
23 -30 -21   6
24 -31 -21   6

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