CODEWITHSUNDEEP
rgeometrypolygon
OKLM
OKLM

Reputation: 95

Create a sfc_GEOMETRY object from a data frame of vectors in R

I am working on creating a custom US map in R. I want to alter one state's geometry to fit how I need it. As a base, I am using the FiveThirtyEight electoral map from the tilegramsR package. Below is the code I use to get all of the states.

library(tilegramsR)
library(dplyr)
States <- sf_FiveThirtyEightElectoralCollege.states

This gives a data frame where the first column is a state and the second is the geometry of the border (it comes out to looking like a bunch of connected hexagons for each state).

I want to replace one of the states' geometry. I already have coordinates, however, it is currently stored in a data frame. The exact coordinates are long, but structure of the data is listed below.

exCoords <- data.frame(V1 = c(1,1,2,2,1),
                       V2 = c(1,2,2,1,1))

The first row is the first set of coordinates, the second is the second (Coordinate 1 (x,y) = exCoords[1, 1], exCoords[1, 2], Coordinate 2 (x,y) = exCoords[2, 1], exCoords[2, 2]) etc. . .

What I want to do is convert the data frame coordinates to a geometry object like in the States frame I am using, and replace one of the states coordinates with the ones I have created. How would I go about that with the new coordinates currently stored as a data frame?

Upvotes: 1

Views: 372

Answers (1)

Andrew Gustar
Andrew Gustar

Reputation: 18425

Each element of the geometry column is simply a two-column matrix wrapped in a list in another list. You can therefore just edit them directly...

States$geometry[n][[1]][[1]] <- as.matrix(exCoords)

where n is the row number of States that you want to replace. All of the sfc_geometry attributes are retained.

Upvotes: 2

Related Questions