title: era Interim data extracting a variable from RNetCDF
body: <p>My goal is extract temperature, date from each latitude and longitude from this ERA interim data file  (see link <a href="https://www.dropbox.com/s/lnxetoy1911q5sg/_grib2netcdf-atls17-95e2cf679cd58ee9b4db4dd119a05a8d-vMTGKo.nc?dl=0" rel="nofollow">https://www.dropbox.com/s/lnxetoy1911q5sg/_grib2netcdf-atls17-95e2cf679cd58ee9b4db4dd119a05a8d-vMTGKo.nc?dl=0</a>) </p>
  
  <p>I am using  RNetCDF package in R but when I used the var.get.nc function my values are all negatives. I am stuck at this step.  I know there is data in the netcdf as I opened it ArcMap. My codes are below</p>
  
  <pre><code>require(RNetCDF)
  nc_in1   = open.nc("_grib2netcdf-atls17-95e2cf679cd58ee9b4db4dd119a05a8d-vMTGKo.nc")
  # get all Air temperature data data:
   temp      &lt;- var.get.nc(nc_in1, "t2m")
  head(temp)
  </code></pre>
  
  <p>-8355 -8399 -8444 -8487 -8531 -8576</p>
  
  <p>#Data structure are as follows</p>
  
  <pre><code>    print.nc(nc_in1)
      dimensions:
      longitude = 561 ;
      latitude = 321 ;
      time = UNLIMITED ; // (8 currently)
      variables:
      float longitude(longitude) ;
              longitude:units = "degrees_east" ;
              longitude:long_name = "longitude" ;
      float latitude(latitude) ;
              latitude:units = "degrees_north" ;
              latitude:long_name = "latitude" ;
      int time(time) ;
              time:units = "hours since 1900-01-01 00:00:0.0" ;
              time:long_name = "time" ;
              time:calendar = "gregorian" ;
      short t2m(longitude, latitude, time) ;
              t2m:scale_factor = 0.001140245 ;
              t2m:add_offset = 264.0577 ;
              t2m:_FillValue = -32767 ;
              t2m:missing_value = -32767 ;
              t2m:units = "K" ;
              t2m:long_name = "2 metre temperature" ;
  
             // global attributes:
              :Conventions = "CF-1.6" ;
              :history = "2016-04-30 18:18:33 GMT by grib_to_netcdf-1.14.5: grib_to_netcdf /data/data01/scratch/_mars-atls02-95e2cf679cd58ee9b4db4dd119a05a8d-E36dti.grib -o /data/data01/scratch/_grib2netcdf-atls17-95e2cf679cd58ee9b4db4dd119a05a8d-vMTGKo.nc -uti
  </code></pre>
  
  <p>I was able to use the same package and codes to achieve the same using MERRA data but I cant seem to find my error in this ERA interim dataset. Any assistance to solve this issue in RNetCDF would be helpful as I am little familiar with this package and still learning about .nc files. </p>