R: divide latitude and longitude into grid sections

Question

I have latitude and longitude points:

> d1 <- data.frame(lat, lon)
> head(d1)
       lat       lon
1 43.25724 -96.01955
2 43.25724 -95.98172
3 43.25724          


        

Answer 1

One way is to use cut on each axis.

set.seed(2)
n <- 50
df <- data.frame(x = runif(n), y = runif(n))
head(df)
#           x           y
# 1 0.1848823 0.007109038
# 2 0.7023740 0.014693911
# 3 0.5733263 0.683403423
# 4 0.1680519 0.929720222
# 5 0.9438393 0.275401199
# 6 0.9434750 0.811859695

Now assign the bins, arbitrarily generating a 3x3 grid:

df <- within(df, {
  grp.x = cut(x, (0:3)/3, labels = FALSE)
  grp.y = cut(y, (0:3)/3, labels = FALSE)
})
head(df)
#           x           y grp.y grp.x
# 1 0.1848823 0.007109038     1     1
# 2 0.7023740 0.014693911     1     3
# 3 0.5733263 0.683403423     3     2
# 4 0.1680519 0.929720222     3     1
# 5 0.9438393 0.275401199     1     3
# 6 0.9434750 0.811859695     3     3

Now these can be used in grouping, coloring, etc. Here's a graph just for demonstration, but indicating that by color (Y-axis) and shape (X-axis), the points can be processed as a group.

plot(y ~ x, data = df, pch = (15:17)[grp.x], col = grp.y)
abline(v = (1:2)/3)
abline(h = (1:2)/3)