In einarhjorleifsson/fishdown: Does not matter.

On spatial operations

Geocomputation

Attribute operations

library(tidyverse)
library(sf)
library(tmap)

fao <- 
  gisland::read_sf_ftp("fao-areas") %>% 
  mutate(area = str_sub(name, 1, 2) %>% as.integer())
fao_na <- 
  fao %>% 
  filter(area %in% c(21, 27))
plot(fao_na["name"])

bb <- st_bbox(fao_na)
n <- 1e3
d <- 
  data_frame(id = 1:n,
             lon = runif(n, bb[[1]], bb[[3]]),
             lat = runif(n,  bb[[2]],  bb[[4]])) %>% 
  st_as_sf(coords = c("lon", "lat"),
           crs = st_crs(fao_na))

Spatial operations

Filter

# Only points inside FAO areas 21 and 27
d2 <- d[fao_na, ]
# same as:
# d2 <- d[fao, , op = st_intersects]
nrow(d2)

# alternatively
sel_sgbp = st_intersects(x = d, y = fao_na)
class(sel_sgbp)
# turn into a logical
i = lengths(sel_sgbp) > 0
d2 = d[i, ]

Getting area attribute for a point:

ices <- 
  fao_na %>% 
  filter(area %in% c(27)) %>% 
  mutate(colval = runif(n()))
plot(ices["name"])


d2 <-
  d %>% 
  st_join(ices %>% select(name, colval))



ggplot(d2) +
  theme_bw() +
  geom_sf(data = ices, aes(fill = colval), alpha = 0.3) +
  geom_sf(aes(colour = colval)) +
  scale_fill_distiller(palette = "Spectral") +
  scale_colour_distiller(palette = "Dark2", direction = -1) +
  theme(legend.position = "none")
table(d2$name, useNA = "ifany")

n <- 1e3
d <- 
  data_frame(id = 1:n,
             lon = runif(n, bb[[1]], bb[[3]]),
             lat = runif(n,  bb[[2]],  bb[[4]])) %>% 
  st_as_sf(coords = c("lon", "lat"),
           crs = st_crs(fao_na))
x <- st_within(d, ices, sparse = TRUE)

# tmap_mode("view")
# p

# # test on larger dataset
# n <- 1e6
# set.seed(2018)
# bb <- st_bbox(ices)
# d <- 
#   tibble(
#   id = 1:n,
#   x = runif(n = n, min = bb[1], max = bb[3]),
#   y = runif(n = n, min = bb[2], max = bb[4])) %>% 
#   st_as_sf(coords = c("x", "y")) %>% 
#   st_set_crs(4326) %>% 
#   st_join(ices["name"])

On CRS

library(tmap)
tmap_options(max.categories = 66)
tm_shape(ices) +
  tm_polygons("name")

einarhjorleifsson/fishdown documentation built on June 26, 2022, 2:31 p.m.