I am having a bit of a problem converting .csv files into raster in R... My .csv file contains coordinates (long and lat) radius (in deg) and site type. I was able to convert the coordinates into raster and was able to plot the circles using st_buffer() but I am facing two problems:
rasterize() and fasterize() and both did not work all I'm getting is an empty raster layerAny idea of what I might be doing wrong? and how can I classify my circles? Thank you in advance!
Here is the code I used:
> head(sp_csv_data)
Longitude Latitude Radius Site_Type
1 -177.87567 -24.715167 10 MIG
2 -83.21360 14.401800 1 OBS
3 -82.59392 9.589192 1 NES
4 -82.41060 9.492750 1 NES;BRE
5 -81.17555 7.196750 5 OBS
6 -80.95770 8.852700 1 NES
##Projection systems used
rob_pacific <- "+proj=robin +lon_0=180 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs" # Best to define these first so you don't make mistakes below
longlat <- "+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0"
####Converting to raster####
# Creating a empty raster at 0.5° resolution (you can increase the resolution to get a better border precision)
rs <- raster(ncol = 360*2, nrow = 180*2)
rs[] <- 1:ncell(rs)
crs(rs) <- CRS(longlat)
##Converting to raster
sp_raster <- rasterize(sp_csv_data[,1:2], rs, sp_csv_data[,3])
# Resampling to make sure that it's in the same resolution as sampling area
sp_raster <- resample(sp_raster, rs, resample = "ngb")
#converting into an sf spatial polygon dataframe
sp_raster <- as(sp_raster, "SpatialPolygonsDataFrame")
species_sp <- spTransform(sp_raster, CRS(longlat))
# Define a long & slim polygon that overlaps the meridian line & set its CRS to match that of world
polygon <- st_polygon(x = list(rbind(c(-0.0001, 90),
c(0, 90),
c(0, -90),
c(-0.0001, -90),
c(-0.0001, 90)))) %>%
st_sfc() %>%
st_set_crs(longlat)
# Transform the species distribution polygon object to a Pacific-centred projection polygon object
sp_robinson <- species_sp %>%
st_as_sf() %>%
st_difference(polygon) %>%
st_transform(crs = rob_pacific)
# There is a line in the middle of Antarctica. This is because we have split the map after reprojection. We need to fix this:
bbox1 <- st_bbox(sp_robinson)
bbox1[c(1,3)] <- c(-1e-5,1e-5)
polygon1 <- st_as_sfc(bbox1)
crosses1 <- sp_robinson %>%
st_intersects(polygon1) %>%
sapply(length) %>%
as.logical %>%
which
# Adding buffer 0
sp_robinson[crosses1, ] %<>%
st_buffer(0)
# Adding the circles to the coordinates
sp_robinson2 <- st_buffer(sp_robinson, dist = radius)
> print(sp_robinson2)
Simple feature collection with 143 features and 1 field
geometry type: POLYGON
dimension: XY
bbox: xmin: -17188220 ymin: -5706207 xmax: 17263210 ymax: 6179000
CRS: +proj=robin +lon_0=180 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs
First 10 features:
layer geometry
1 5 POLYGON ((3556791 4766657, ...
2 10 POLYGON ((13713529 4995696,...
3 10 POLYGON ((12834403 4946927,...
4 10 POLYGON ((9991443 4801974, ...
5 5 POLYGON ((4254202 4304190, ...
6 5 POLYGON ((11423719 4327354,...
7 10 POLYGON ((9582710 4282247, ...
8 10 POLYGON ((588877.2 4166512,...
9 5 POLYGON ((4522824 3894919, ...
10 10 POLYGON ((3828685 3886205, ...
sp_robinson3 <- fasterize(sp_robinson2, rs)
> print(sp_robinson3)
class : RasterLayer
dimensions : 360, 720, 259200 (nrow, ncol, ncell)
resolution : 0.5, 0.5 (x, y)
extent : -180, 180, -90, 90 (xmin, xmax, ymin, ymax)
crs : +proj=robin +lon_0=180 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs
source : memory
names : layer
values : NA, NA (min, max)
I want to convert sp_robinson2 into a raster called sp_robinson3 but as you can see both fasterize()and rasterize()are giving me an empty raster layer...
The reason why rasterize does not work in the end is obvious: the crs of the vector and raster do not match. But can you edit your question a bit more to explain what you want to achieve? It is very odd to create a raster and then polygons and then rasterize these again. My impression is that you are making things much more complicated than need be. You also talk about circles. Which circles? I am guessing you may want circles around your points, but that is not what you are doing. It would probably be helpful to figure out things step by step, first figure out how to get the general result you want, then how to get it Pacific centered.
Below is a cleaned up version of the first part of your code. It also makes it reproducible. You need to create example in code, like this:
lon <- c(-177.87567, -83.2136, -82.59392, -82.4106, -81.17555, -80.9577)
lat <- c(-24.715167, 14.4018, 9.589192, 9.49275, 7.19675, 8.8527)
radius <- c(10, 1, 1, 1, 5, 1)
site <- c("MIG", "OBS", "NES", "NES;BRE", "OBS", "NES")
sp_csv_data <- data.frame(lon, lat, radius, site)
## cleaned up projection definitions
rob_pacific <- "+proj=robin +lon_0=180 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs"
longlat <- "+proj=longlat +datum=WGS84"
##Converting to raster
# Creating a empty raster at 0.5° resolution
rs <- raster(res=0.5, crs=lonlat)
values(rs) <- 1:ncell(rs)
sp_raster <- rasterize(sp_csv_data[,1:2], rs, sp_csv_data[,3])
## makes no sense: sp_raster <- resample(sp_raster, rs, resample = "ngb")
#converting into an SpatialPolygonsDataframe
species_sp <- as(sp_raster, "SpatialPolygonsDataFrame")
## makes no sense: species_sp <- spTransform(sp_raster, CRS(longlat))