Notes on concatenation issue

concatenation_dim_order_issue

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 "worksheets": [
  {
   "cells": [
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "import iris\n",
      "import iris.coords\n",
      "import iris.cube\n",
      "import numpy as np"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 1
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Create some dummy data consisting of two cubes, one with a length-2 time dimension and one with a length-1 time dimension. The cubes have matching metadata, as do their coordinates."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "time0 = iris.coords.DimCoord([0., 1.], units='days since 2000-01-01', standard_name='time')\n",
      "time1 = iris.coords.DimCoord([2.], units='days since 2000-01-01', standard_name='time')\n",
      "\n",
      "lat = iris.coords.DimCoord([-10., 0., 10.], standard_name='latitude', units='degrees_north')\n",
      "lon = iris.coords.DimCoord([20., 40., 60., 80.], standard_name='longitude', units='degrees_east')\n",
      "\n",
      "cube0 = iris.cube.Cube(np.random.random([2, 3, 4]), standard_name='air_temperature', units='K',\n",
      "                       dim_coords_and_dims=[(time0, 0), (lat, 1), (lon, 2)])\n",
      "cube1 = iris.cube.Cube(np.random.random([1, 3, 4]), standard_name='air_temperature', units='K',\n",
      "                       dim_coords_and_dims=[(time1, 0), (lat, 1), (lon, 2)])\n",
      "\n",
      "cubes = iris.cube.CubeList([cube0, cube1])\n",
      "print(cubes)"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "0: air_temperature / (K)               (time: 2; latitude: 3; longitude: 4)\n",
        "1: air_temperature / (K)               (time: 1; latitude: 3; longitude: 4)\n"
       ]
      }
     ],
     "prompt_number": 2
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Attempt to concatenate the cubes, this works..."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "cubes.concatenate_cube()"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 3,
       "text": [
        "<iris 'Cube' of air_temperature / (K) (time: 3; latitude: 3; longitude: 4)>"
       ]
      }
     ],
     "prompt_number": 3
    },
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "Inspect the `dim_order` attribute, it looks the same as the reported issue, but in this case the concatenation works as expected."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "from iris._concatenate import _CoordSignature, _CubeSignature\n",
      "cube_signatures = [_CubeSignature(cube) for cube in cubes]\n",
      "coord_signatures = [_CoordSignature(cube_sig) for cube_sig in cube_signatures]\n",
      "print coord_signatures[0].dim_order\n",
      "print coord_signatures[1].dim_order"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "output_type": "stream",
       "stream": "stdout",
       "text": [
        "[1, 1, 1]\n",
        "[0, 1, 1]\n"
       ]
      }
     ],
     "prompt_number": 4
    }
   ],
   "metadata": {}
  }
 ]
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