Access Parameter Values from getTerraClim Output for 900 Counties

[MengyaTao]

Hi Mike,

I am trying to use function 'getTerraClim', but I am not familiar with the output data structure. Do you know what the commands would be if I want to access parameter values only? Is this something like 'tc$prcp@something'? So I can then be able to save them in .csv in R.

Here is the google drive link to all the counties (.shp file) that I would like to access their parameters from TerraClimate data source: https://drive.google.com/file/d/1y_NN771ch-YS4nSNH6pXes40iELAnR-i/view?usp=sharing

Thank you! Mengya

[mikejohnson51]

Hi,

From my understanding, you are looking to get an areal average for each of your 891 counties from the TerraClim dataset for all months in 2010. To do this I would loop through the counties using the for each package, here is an example for 'aet'. The trick here is to account for the area of each county yielding a mm/km2 value:

#Define your path 
path = './corn_890_counties.shp'
# Read in your county object
z = read_sf(path)
#Specify a parameter
params = 'aet'

system.time({
    `%dopar%` <- foreach::`%dopar%`
    no_cores  <- parallel::detectCores() - 1
    doParallel::registerDoParallel(no_cores)

    var = foreach::foreach(i = 1:NROW(z),.combine = 'rbind', .packages = 'climateR') %dopar% {
      #assign area in km2                  
      if(param %in% c('tmax', 'tmin')) { area = 1 } else { area = as.numeric(st_area(z[i,]) / 1e6)}

      #get data for county in 2010
      r = getTerraClim(z[i, ],  param = params,  startDate = '2010')

       # calculate mean of each raster layer and append to county FIP code     
      c(as.numeric(z$GEOID[i]),  (cellStats(r[[1]], stat = 'mean', na.rm = TRUE) * area))
     }

    # rename
    colnames(var) = c("GEOID", month.abb)
    row.names(var) = NULL
    # write to csv in the same folder as your shp
    write.csv(var, paste0(dirname(path), "/", params, ".csv"))
})

   user  system elapsed 
 56.238   8.957 114.668 

Hope that helps!

Mike

[MengyaTao]

Thank you so much!!!