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  {
   "cells": [
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "# testing stride on NOMADS\n",
      "Trying to figure out why this NCO ncks stride command doesn't work:\n",
      "```\n",
      "ncks -O -D4 -d time,1 -d lev,0 -d lat,0,100,3 -d lon,0,100,3 -v u_velocity,v_velocity \\\n",
      " http://nomads.ncep.noaa.gov:9090/dods/rtofs/rtofs_global20140303/rtofs_glo_2ds_forecast_daily_prog foo.nc\n",
      "```\n",
      "Does it work with netCDF4-Python, which also uses the NetCDF-C library?"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "import netCDF4"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 1
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "url='http://nomads.ncep.noaa.gov:9090/dods/rtofs/rtofs_global20140303/rtofs_glo_2ds_forecast_daily_prog'\n"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 2
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "nc = netCDF4.Dataset(url)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 3
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "ncv = nc.variables"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 4
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Try just reading a few values of longitude"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "ncv['lon'][:10]"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 5,
       "text": [
        "array([ 74.16   ,  74.24333,  74.32666,  74.40999,  74.49332,  74.57665,\n",
        "        74.65998,  74.74331,  74.82664,  74.90997])"
       ]
      }
     ],
     "prompt_number": 5
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Now try reading the u_velocity variable with stride"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "u = ncv['u_velocity'][0,0,0:100:3,0:100:3]\n",
      "v = ncv['v_velocity'][0,0,0:100:3,0:100:3]\n",
      "print shape(u)\n",
      "print shape(v)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "(34, 34)\n",
        "(34, 34)\n"
       ]
      }
     ],
     "prompt_number": 6
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Seems to work fine.  Why doesn't NCO work?"
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 6
    }
   ],
   "metadata": {}
  }
 ]
}