title: Error reading a .nc4 file in R (ncdf4 package)
body: <p>I am trying to use a data set of <code>.nc4 files</code> downloaded from <a href="http://mirador.gsfc.nasa.gov/" rel="nofollow">NASA</a>. </p>
  
  <p>The format NCDF4 is confirmed by <a href="http://disc.gsfc.nasa.gov/uui/datasets/GLDAS_NOAH025_M_V2.0/summary?keywords=GLDAS_NOAH025_M_2.0&amp;start=1920-01-01&amp;end=2016-10-31#prod-summary" rel="nofollow">this source</a>. 
  I used download .file in R to get the database and then a simple nc_open (ncdf4 package) to test the file. Unfortunately the result is an "Unknown file format" error.</p>
  
  <p>Here my <a href="https://www.dropbox.com/s/4efdbfvqm6arjsy/file.nc4?dl=0" rel="nofollow">replication file</a> and my script:</p>
  
  <pre><code>download.file (url=http://hydro1.gesdisc.eosdis.nasa.gov/.../url, destfile=destination_folder/file.nc4)
  </code></pre>
  
  <p>All fine till this point, but when testing the files:</p>
  
  <pre><code>library(ncdf4)
  setwd('destination_folder')
  data &lt;- nc_open('file.nc4')
  Error in R_nc4_open: NetCDF: Unknown file format
   Error in nc_open("file.nc4") : 
   Error in nc_open trying to open file file.nc4
  </code></pre>
  
  <p>Am I missing something?<br>
  Thank you. </p>