Make polygons from a data frame of spatial coordinates
Arguments
- df
A data frame spatial coordinates
- x
Name of column with x coordinates (e.g., longitude). Must be in order.
- y
Name of column with y coordinates (e.g., latitude). Must be in order.
- grp.cols
Index columns for dplyr::group_by. Must index at least one variable, which will be used to identify polygons.
- crs
The coordinate reference system to assign
Examples
x<-c(-65,-60,-55, -61,-60,-59)
y<-c( 47, 50, 47, 48, 49, 48)
grp<-c(rep('big triangle',3),rep('small triangle',3))
source<-c(1,1,1,3,3,3)
d<-cbind.data.frame(x,y,grp,source)
d
#> x y grp source
#> 1 -65 47 big triangle 1
#> 2 -60 50 big triangle 1
#> 3 -55 47 big triangle 1
#> 4 -61 48 small triangle 3
#> 5 -60 49 small triangle 3
#> 6 -59 48 small triangle 3
pol<-make_polygon(d,'x','y',c('grp','source'),4326)
terra::plot(pol)
