trees.ipynb

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   "source": [
    "from math import log\n",
    "def calcShannonEnt(dataSet):\n",
    "    numEntries = len(dataSet)\n",
    "    labelCounts = {}\n",
    "    for featVec in dataSet:\n",
    "        currentLabel = featVec[-1]\n",
    "        if currentLabel not in labelCounts.keys(): labelCounts[currentLabel] = 0\n",
    "        labelCounts[currentLabel] += 1\n",
    "    shannonEnt = 0.0\n",
    "    for key in labelCounts:\n",
    "        prob = float(labelCounts[key]) / numEntries\n",
    "        shannonEnt -= prob * log(prob,2)\n",
    "    return shannonEnt\n",
    "\n",
    "def createDataSet():\n",
    "    dataSet = ([[1,1,'yes'], [1,1,'yes'],\n",
    "                [1,0,'no'],  [0,1,'no'],\n",
    "                [0,1,'no']])\n",
    "    labels = ['no surfacing','flippers']\n",
    "    return dataSet, labels\n",
    "\n",
    "def splitDataSet(dataSet, axis, value):\n",
    "    retDataSet = []\n",
    "    for featVec in dataSet:\n",
    "        if featVec[axis] == value:\n",
    "            reducedFeatVec = featVec[:axis]\n",
    "            reducedFeatVec.extend(featVec[axis+1:])\n",
    "            retDataSet.append(reducedFeatVec)\n",
    "    return retDataSet\n"
   ]
  },
  {
   "cell_type": "code",
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    {
     "ename": "NameError",
     "evalue": "name 'trees' is not defined",
     "output_type": "error",
     "traceback": [
      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
      "\u001b[0;31mNameError\u001b[0m                                 Traceback (most recent call last)",
      "\u001b[0;32m<ipython-input-6-20aa0a12050d>\u001b[0m in \u001b[0;36m<module>\u001b[0;34m()\u001b[0m\n\u001b[0;32m----> 1\u001b[0;31m \u001b[0mreload\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0mtrees\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mpy\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n\u001b[0m\u001b[1;32m      2\u001b[0m \u001b[0mmyDat\u001b[0m\u001b[0;34m,\u001b[0m \u001b[0mlabels\u001b[0m \u001b[0;34m=\u001b[0m \u001b[0mtrees\u001b[0m\u001b[0;34m.\u001b[0m\u001b[0mcreateDataSet\u001b[0m\u001b[0;34m(\u001b[0m\u001b[0;34m)\u001b[0m\u001b[0;34m\u001b[0m\u001b[0m\n",
      "\u001b[0;31mNameError\u001b[0m: name 'trees' is not defined"
     ]
    }
   ],
   "source": [
    "import trees\n",
    "myDat, labels = trees.createDataSet()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": []
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