Fast grouper.ipynb

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     "cell_type": "code",
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     "input": [
      "import numpy as np"
     ],
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     "metadata": {},
     "outputs": [],
     "prompt_number": 146
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "t = np.arange(0, 40, 2)\n",
      "t"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 147,
       "text": [
        "array([ 0,  2,  4,  6,  8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32,\n",
        "       34, 36, 38])"
       ]
      }
     ],
     "prompt_number": 147
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "a = np.random.randint(-10, 10, 20)\n",
      "a"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 148,
       "text": [
        "array([ 6, -4, -7, -1, -9,  2, -8,  8, -6,  9, -5, -5,  7, -9,  4,  9,  4,\n",
        "        0,  3,  5])"
       ]
      }
     ],
     "prompt_number": 148
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "b = np.zeros(a.shape)\n",
      "b[a > 0] = 1\n",
      "b"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 149,
       "text": [
        "array([ 1.,  0.,  0.,  0.,  0.,  1.,  0.,  1.,  0.,  1.,  0.,  0.,  1.,\n",
        "        0.,  1.,  1.,  1.,  0.,  1.,  1.])"
       ]
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     ],
     "prompt_number": 149
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "c = np.roll(b, -1)\n",
      "c"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 150,
       "text": [
        "array([ 0.,  0.,  0.,  0.,  1.,  0.,  1.,  0.,  1.,  0.,  0.,  1.,  0.,\n",
        "        1.,  1.,  1.,  0.,  1.,  1.,  1.])"
       ]
      }
     ],
     "prompt_number": 150
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "d = b - c\n",
      "d"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 151,
       "text": [
        "array([ 1.,  0.,  0.,  0., -1.,  1., -1.,  1., -1.,  1.,  0., -1.,  1.,\n",
        "       -1.,  0.,  0.,  1., -1.,  0.,  0.])"
       ]
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     "prompt_number": 151
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "e = np.where(d != 0)[0]\n",
      "if e[0] != 0:\n",
      "    e = np.insert(e, 0, 0)\n",
      "e"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 152,
       "text": [
        "array([ 0,  4,  5,  6,  7,  8,  9, 11, 12, 13, 16, 17])"
       ]
      }
     ],
     "prompt_number": 152
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "f = np.roll(e, -1)\n",
      "f[-1] = a.shape[0]\n",
      "f"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
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       "prompt_number": 153,
       "text": [
        "array([ 4,  5,  6,  7,  8,  9, 11, 12, 13, 16, 17, 20])"
       ]
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     "prompt_number": 153
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "g = f - e\n",
      "g"
     ],
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     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 154,
       "text": [
        "array([4, 1, 1, 1, 1, 1, 2, 1, 1, 3, 1, 3])"
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     ],
     "prompt_number": 154
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "g.sum()"
     ],
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       "prompt_number": 155,
       "text": [
        "20"
       ]
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     "prompt_number": 155
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     "collapsed": false,
     "input": [
      "h = np.repeat(e, g)\n",
      "h"
     ],
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     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 156,
       "text": [
        "array([ 0,  0,  0,  0,  4,  5,  6,  7,  8,  9,  9, 11, 12, 13, 13, 13, 16,\n",
        "       17, 17, 17])"
       ]
      }
     ],
     "prompt_number": 156
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "i = h - np.arange(a.shape[0])\n",
      "i"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 161,
       "text": [
        "array([ 0, -1, -2, -3,  0,  0,  0,  0,  0,  0, -1,  0,  0,  0, -1, -2,  0,\n",
        "        0, -1, -2])"
       ]
      }
     ],
     "prompt_number": 161
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "start = t[i + np.arange(a.shape[0])]\n",
      "start"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 162,
       "text": [
        "array([ 0,  0,  0,  0,  8, 10, 12, 14, 16, 18, 18, 22, 24, 26, 26, 26, 32,\n",
        "       34, 34, 34])"
       ]
      }
     ],
     "prompt_number": 162
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "current = t\n",
      "current"
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     "metadata": {},
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      {
       "metadata": {},
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       "prompt_number": 163,
       "text": [
        "array([ 0,  2,  4,  6,  8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32,\n",
        "       34, 36, 38])"
       ]
      }
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     "prompt_number": 163
    },
    {
     "cell_type": "code",
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     "input": [
      "delta = current - start\n",
      "delta"
     ],
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     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 164,
       "text": [
        "array([0, 2, 4, 6, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 2, 4, 0, 0, 2, 4])"
       ]
      }
     ],
     "prompt_number": 164
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     "input": [
      "def fast_group(a, t):\n",
      "    # Anything greater than 0 should be 1.\n",
      "    b = np.zeros(a.shape)\n",
      "    b[a > 0.] = 1\n",
      "    \n",
      "    # Find leading and trailing edges.\n",
      "    d = b - np.roll(b, -1)\n",
      "    d = np.roll(d, 1)\n",
      "    \n",
      "    # Get indicies of the edges.  Make sure 0 is an edge.\n",
      "    e = np.where(d != 0)[0]\n",
      "    if e[0] != 0:\n",
      "        e = np.insert(e, 0, 0)\n",
      "    \n",
      "    # Calc the length of each segment usings edge indicies.\n",
      "    f = np.roll(e, -1)\n",
      "    f[-1] = a.shape[0]\n",
      "    g = f - e\n",
      "    \n",
      "    # Repeat the edge indicies for the segment lengths.\n",
      "    h = np.repeat(e, g)\n",
      "    \n",
      "    # Get the segment start times\n",
      "    i = h - np.arange(a.shape[0])\n",
      "    start = t[i + np.arange(a.shape[0])]\n",
      "    \n",
      "    # Return the delta from the last start time.\n",
      "    return t - start"
     ],
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     "metadata": {},
     "outputs": [],
     "prompt_number": 165
    },
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     "input": [
      "a = np.random.randint(-10, 10, 20)\n",
      "t = np.arange(20)\n",
      "fast_group(a,t)"
     ],
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     "metadata": {},
     "outputs": [
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       "metadata": {},
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       "prompt_number": 218,
       "text": [
        "array([0, 0, 1, 2, 3, 0, 1, 2, 0, 1, 2, 3, 4, 0, 1, 0, 0, 0, 0, 0])"
       ]
      }
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     "prompt_number": 218
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