add soil ph from soilgrid
use the folowing functions
# Functions to extract soil data from
# ftp://ftp.soilgrids.org/data/archive/12.Apr.2014/
## TODO change for ftp://ftp.soilgrids.org/data/aggregated/1km/ for sl1 and sl2 and take the mean
extract_ph <- function(lats, lons, dir_temp = "soil_temp"){
require(raster)
require(R.utils)
# download raster
url_ph <- "ftp://soilgrids:soilgrids@ftp.soilgrids.org/data/archive/12.Apr.2014/PHIHOX_sd2_M_02_apr_2014.tif.gz"
raster_name_gz <- "PHIHOX_sd2_M_02_apr_2014.tif.gz"
raster_name <- "PHIHOX_sd2_M_02_apr_2014.tif"
if(!file.exists(file.path(dir_temp, raster_name))){
dir.create(dir_temp)
download.file(url_ph, file.path(dir_temp, raster_name_gz),mode="wb")
gunzip(file.path(dir_temp, raster_name_gz))
}
# load raster
raster_ph <- raster(file.path(dir_temp, raster_name))
plot_ph <- raster::extract(raster_ph, cbind(lons, lats))/10
return(plot_ph)
}