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rdownloadnetcdf

Downloading NetCDF files with R: Manually works but the downloaded file is smaller

I am trying to download NetCDF files from: https://ftp.cpc.ncep.noaa.gov/NMME/prob/netcdf/

When I manually download the files I got a file of about 5000 Kb, when it is downloaded with the code below I got a file of 119 Kb and it is not usable.

now <- as.Date(Sys.Date())
now <- paste0(substr(now,1,4),substr(now,6,7))
filename <- paste0('prate.',now,'.prob.adj.seas',".nc")
root <- 'https://ftp.cpc.ncep.noaa.gov/NMME/prob/netcdf/'
download.file(root, filename,mode = "wb")

Any suggestion? Thanks

Solution

  • You use the arguments of download.file() incorrectly. Try

    ## your code
now <- as.Date(Sys.Date())
now <- paste0(substr(now,1,4),substr(now,6,7))
filename <- paste0('prate.',now,'.prob.adj.seas',".nc")
root <- 'https://ftp.cpc.ncep.noaa.gov/NMME/prob/netcdf/' # main_url

## changes
path <- getwd() # example of donwload directory
download.file(url = paste0(root, filename), 
              destfile = file.path(path, basename(filename)))

    See ?download.file

    1. The first argument to download.file() is a url, i.e., "https://ftp.cpc.ncep.noaa.gov/NMME/prob/netcdf/prate.202311.prob.adj.seas.nc".
    2. Then specify destfile, i.e., the local path, a combination of download directory and file name. On Mac OS X it looks like "/Users/YourUsername/Desktop/prate.202311.prob.adj.seas.nc".
    download.file(url = paste0(root, filename), 
              destfile = file.path(path, basename(filename)))

    equals

    download.file(
  url = "https://ftp.cpc.ncep.noaa.gov/NMME/prob/netcdf/prate.202311.prob.adj.seas.nc",
  destfile = "/Users/YourUsername/Desktop/prate.202311.prob.adj.seas.nc")

    I think mode = "wb" is not necessary. Haven't checked.