In RobinKohrs/rainfallR: Extract and manipulate gridded rainfall measurements

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)

Intro

This is a small example that shows how to extract rainfall data for vector-polygons.
First we need to load the packages and set some paths

library(rainfallR)
library(stars)
library(ncdf4)
library(tidyverse)
library(scales)
library(raster)
library(sf)

Now we can set some paths
We will use the gridded rainfall data and a manually created polygon

os = Sys.info()["sysname"]

if(os == "Linux"){
  path_data = "/mnt/CEPH_PROJECTS/Proslide/PREC_GRIDS_updated/"
  su_path = "/mnt/CEPH_PROJECTS/Proslide/Envir_data/SlopeUnits/su_opt_16_TAA/su_16_TAA.shp" 
}else{
  # the path to the data
  path_data = "\\\\projectdata.eurac.edu/projects/Proslide/PREC_GRIDS_updated/"
  # path to the slop units
  su_path = "\\\\projectdata.eurac.edu/projects/Proslide/Envir_data/SlopeUnits/su_opt_16_TAA/su_16_TAA.shp"
}

Next we set some parameters in order to extract the data from the rainfallR::get_rainfall-function

# set some parameters for the rainfallR
day = as.Date("2016-08-16")

# get the day as integer
day_int = format(day, "%d")

# we only want one raster to get the bounding box in order to draw s shape
days_back = 1

# create the path to the NetCDF
path_ncdf = rainfallR::get_nc_paths(path_data, day, days_back) %>% .[[1]]

# read in one raster with stars
r = read_ncdf(path_ncdf) 

# extract one raster
r = r[,,,16]

Now that we have one raster, let's create a shape

set.seed(2)

# read in the slope units and select a random one
su = read_sf(su_path)

# select a random one
su = su %>% slice(sample(1:nrow(su), 1))

Extract the rainfall for one date for that polygon

We now have:
the path to the NetCdfs
a spatial vector object
a date we want to extract the rainfall data
We can now query the rainfall data as a table with the rainfallR-package

rainfall = rainfallR::ex_rainfall(
  data_path = path_data,
  spatial.obj = su,
  date = day,
  fun = c("mean", "max"),
  days_back = 3
)

# what have we got?
print(rainfall)