pandas_group_rows_by.ipynb

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  {
   "cells": [
    {
     "cell_type": "markdown",
     "metadata": {},
     "source": [
      "# Grouping Rows In Pandas\n",
      "\n",
      "This snippit was written by [Chris R. Albon](http://www.chrisralbon.com/) and is part of his collection of [well-documented Python snippits](https://github.com/chrisalbon/code_py). All code is written in Python 3 in iPython notebook and offered under the [Creative Commons Attribution-ShareAlike 4.0 International License](http://creativecommons.org/licenses/by-sa/4.0/\"><img alt=\"Creative Commons License)."
     ]
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Import modules\n",
      "import pandas as pd"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 9
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Example dataframe\n",
      "raw_data = {'regiment': ['Nighthawks', 'Nighthawks', 'Nighthawks', 'Nighthawks', 'Dragoons', 'Dragoons', 'Dragoons', 'Dragoons', 'Scouts', 'Scouts', 'Scouts', 'Scouts'], \n",
      "        'company': ['1st', '1st', '2nd', '2nd', '1st', '1st', '2nd', '2nd','1st', '1st', '2nd', '2nd'], \n",
      "        'name': ['Miller', 'Jacobson', 'Ali', 'Milner', 'Cooze', 'Jacon', 'Ryaner', 'Sone', 'Sloan', 'Piger', 'Riani', 'Ali'], \n",
      "        'preTestScore': [4, 24, 31, 2, 3, 4, 24, 31, 2, 3, 2, 3],\n",
      "        'postTestScore': [25, 94, 57, 62, 70, 25, 94, 57, 62, 70, 62, 70]}\n",
      "df = pd.DataFrame(raw_data, columns = ['regiment', 'company', 'name', 'preTestScore', 'postTestScore'])\n",
      "df"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "html": [
        "<div style=\"max-height:1000px;max-width:1500px;overflow:auto;\">\n",
        "<table border=\"1\" class=\"dataframe\">\n",
        "  <thead>\n",
        "    <tr style=\"text-align: right;\">\n",
        "      <th></th>\n",
        "      <th>regiment</th>\n",
        "      <th>company</th>\n",
        "      <th>name</th>\n",
        "      <th>preTestScore</th>\n",
        "      <th>postTestScore</th>\n",
        "    </tr>\n",
        "  </thead>\n",
        "  <tbody>\n",
        "    <tr>\n",
        "      <th>0 </th>\n",
        "      <td> Nighthawks</td>\n",
        "      <td> 1st</td>\n",
        "      <td>   Miller</td>\n",
        "      <td>  4</td>\n",
        "      <td> 25</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>1 </th>\n",
        "      <td> Nighthawks</td>\n",
        "      <td> 1st</td>\n",
        "      <td> Jacobson</td>\n",
        "      <td> 24</td>\n",
        "      <td> 94</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>2 </th>\n",
        "      <td> Nighthawks</td>\n",
        "      <td> 2nd</td>\n",
        "      <td>      Ali</td>\n",
        "      <td> 31</td>\n",
        "      <td> 57</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>3 </th>\n",
        "      <td> Nighthawks</td>\n",
        "      <td> 2nd</td>\n",
        "      <td>   Milner</td>\n",
        "      <td>  2</td>\n",
        "      <td> 62</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>4 </th>\n",
        "      <td>   Dragoons</td>\n",
        "      <td> 1st</td>\n",
        "      <td>    Cooze</td>\n",
        "      <td>  3</td>\n",
        "      <td> 70</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>5 </th>\n",
        "      <td>   Dragoons</td>\n",
        "      <td> 1st</td>\n",
        "      <td>    Jacon</td>\n",
        "      <td>  4</td>\n",
        "      <td> 25</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>6 </th>\n",
        "      <td>   Dragoons</td>\n",
        "      <td> 2nd</td>\n",
        "      <td>   Ryaner</td>\n",
        "      <td> 24</td>\n",
        "      <td> 94</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>7 </th>\n",
        "      <td>   Dragoons</td>\n",
        "      <td> 2nd</td>\n",
        "      <td>     Sone</td>\n",
        "      <td> 31</td>\n",
        "      <td> 57</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>8 </th>\n",
        "      <td>     Scouts</td>\n",
        "      <td> 1st</td>\n",
        "      <td>    Sloan</td>\n",
        "      <td>  2</td>\n",
        "      <td> 62</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>9 </th>\n",
        "      <td>     Scouts</td>\n",
        "      <td> 1st</td>\n",
        "      <td>    Piger</td>\n",
        "      <td>  3</td>\n",
        "      <td> 70</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>10</th>\n",
        "      <td>     Scouts</td>\n",
        "      <td> 2nd</td>\n",
        "      <td>    Riani</td>\n",
        "      <td>  2</td>\n",
        "      <td> 62</td>\n",
        "    </tr>\n",
        "    <tr>\n",
        "      <th>11</th>\n",
        "      <td>     Scouts</td>\n",
        "      <td> 2nd</td>\n",
        "      <td>      Ali</td>\n",
        "      <td>  3</td>\n",
        "      <td> 70</td>\n",
        "    </tr>\n",
        "  </tbody>\n",
        "</table>\n",
        "</div>"
       ],
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 14,
       "text": [
        "      regiment company      name  preTestScore  postTestScore\n",
        "0   Nighthawks     1st    Miller             4             25\n",
        "1   Nighthawks     1st  Jacobson            24             94\n",
        "2   Nighthawks     2nd       Ali            31             57\n",
        "3   Nighthawks     2nd    Milner             2             62\n",
        "4     Dragoons     1st     Cooze             3             70\n",
        "5     Dragoons     1st     Jacon             4             25\n",
        "6     Dragoons     2nd    Ryaner            24             94\n",
        "7     Dragoons     2nd      Sone            31             57\n",
        "8       Scouts     1st     Sloan             2             62\n",
        "9       Scouts     1st     Piger             3             70\n",
        "10      Scouts     2nd     Riani             2             62\n",
        "11      Scouts     2nd       Ali             3             70"
       ]
      }
     ],
     "prompt_number": 14
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Create a grouping object. In other words, create an object that\n",
      "# represents that particular grouping. In this case we group\n",
      "# pre-test scores by the regiment.\n",
      "regiment_preScore = df['preTestScore'].groupby(df['regiment'])"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [],
     "prompt_number": 15
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [
      "# Display the mean value of the each regiment's pre-test score\n",
      "regiment_preScore.mean()"
     ],
     "language": "python",
     "metadata": {},
     "outputs": [
      {
       "metadata": {},
       "output_type": "pyout",
       "prompt_number": 16,
       "text": [
        "regiment\n",
        "Dragoons      15.50\n",
        "Nighthawks    15.25\n",
        "Scouts         2.50\n",
        "dtype: float64"
       ]
      }
     ],
     "prompt_number": 16
    },
    {
     "cell_type": "code",
     "collapsed": false,
     "input": [],
     "language": "python",
     "metadata": {},
     "outputs": []
    }
   ],
   "metadata": {}
  }
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