title: Change data source from THREDDS Catalouge for NetCDF
body: <p>Hi i am using this code from here <a href="https://stackoverflow.com/a/28430599/9234311">How to read NetCDF file and write to CSV using Python</a> I want to be able to pull out the "Mean_period_of_swell_waves_ordered_sequence_of_data" from from the <a href="http://thredds.ucar.edu/thredds/dodsC/grib/NCEP/WW3/Global/Best.html" rel="nofollow noreferrer">THREDDS Catalog here</a> but am recieving the below error. I am using Canopy</p>
  
  <p>Any ideas why?
  Thanks Alec</p>
  
  <pre><code>IndexErrorTraceback (most recent call last)
  /home/GRIB-extract-SWPER.py in &lt;module&gt;()
       73 #vname = 'surf_el'
       74 var = nc.variables[vname]
  ---&gt; 75 hs = var[istart:istop,iy,ix]
       76 tim = dtime[istart:istop]
       77 
  netCDF4/_netCDF4.pyx in netCDF4._netCDF4.Variable.__getitem__ (netCDF4/_netCDF4.c:39739)()
  netCDF4/_netCDF4.pyx in netCDF4._netCDF4.Variable._get (netCDF4/_netCDF4.c:49789)()
  IndexError: 
  </code></pre>