{
  "id": 384342,
  "title": "What dose `index` in train.csv actually mean?",
  "url": "/competitions/predict-student-performance-from-game-play/discussion/384342",
  "author_name": "",
  "post_date": "2023-02-07T15:14:00.905481100Z",
  "votes": 16,
  "comment_count": 4,
  "views": 0,
  "content": "<p>In <a href=\"https://www.kaggle.com/competitions/predict-student-performance-from-game-play/data\" target=\"_blank\">Data tab</a>, <code>index</code> is explained as follows.</p>\n<blockquote>\n  <p><strong>index</strong> - the index of the event for the session</p>\n</blockquote>\n<p>But I have 2 questions about this column.</p>\n<p>First, I had assumed that each row in train.csv can be distinguished uniquely with <code>session_id</code> and <code>index</code>, but actually there are some duplication in \"train.csv\" (you can see that next Python code will return 17215 rows).</p>\n<pre><code>df = pd.read_csv(, usecols=[, ])\ndf[df.duplicated(subset=[, ])]\n</code></pre>\n<p>Is this just a data bug or I misunderstood data definition?</p>\n<p>Secondly, I cannot understand the relation between <code>index</code> and <code>elapsed_time</code>. I had assumed that <code>index</code> represents event order in the session, but I found that <code>index</code> and <code>elapsed_time</code> orders are inconsistent in many <code>session_id</code>s.</p>\n<p>Shortly, I cannot understand what this column represents! Could you please share your idea?</p>",
  "messages": [
    {
      "id": "2133727",
      "postDate": "02/07/2023 15:14:00",
      "content": "<p>In <a href=\"https://www.kaggle.com/competitions/predict-student-performance-from-game-play/data\" target=\"_blank\">Data tab</a>, <code>index</code> is explained as follows.</p>\n<blockquote>\n  <p><strong>index</strong> - the index of the event for the session</p>\n</blockquote>\n<p>But I have 2 questions about this column.</p>\n<p>First, I had assumed that each row in train.csv can be distinguished uniquely with <code>session_id</code> and <code>index</code>, but actually there are some duplication in \"train.csv\" (you can see that next Python code will return 17215 rows).</p>\n<pre><code>df = pd.read_csv(, usecols=[, ])\ndf[df.duplicated(subset=[, ])]\n</code></pre>\n<p>Is this just a data bug or I misunderstood data definition?</p>\n<p>Secondly, I cannot understand the relation between <code>index</code> and <code>elapsed_time</code>. I had assumed that <code>index</code> represents event order in the session, but I found that <code>index</code> and <code>elapsed_time</code> orders are inconsistent in many <code>session_id</code>s.</p>\n<p>Shortly, I cannot understand what this column represents! Could you please share your idea?</p>",
      "rawMarkdown": "In [Data tab](https://www.kaggle.com/competitions/predict-student-performance-from-game-play/data), `index` is explained as follows.\n\n> **index** - the index of the event for the session\n\nBut I have 2 questions about this column.\n\nFirst, I had assumed that each row in train.csv can be distinguished uniquely with `session_id` and `index`, but actually there are some duplication in \"train.csv\" (you can see that next Python code will return 17215 rows).\n\n```python\ndf = pd.read_csv(\"/kaggle/input/predict-student-performance-from-game-play/train.csv\", usecols=[\"session_id\", \"index\"])\ndf[df.duplicated(subset=[\"session_id\", \"index\"])]\n```\n\nIs this just a data bug or I misunderstood data definition?\n\nSecondly, I cannot understand the relation between `index` and `elapsed_time`. I had assumed that `index` represents event order in the session, but I found that `index` and `elapsed_time` orders are inconsistent in many `session_id`s.\n\nShortly, I cannot understand what this column represents! Could you please share your idea?",
      "votes": null
    },
    {
      "id": "2133948",
      "postDate": "02/07/2023 17:22:32",
      "content": "<p>I have the same question. For the first question:<br>\nAccording to my observation, If this <code>index == 0</code> indicates that the session starts , there are <code>11769</code> sessions, but the unique <code>session_id</code> is <code>11779</code>, which means that at least <code>10</code> session not start from <code>index == 0</code>. And I also find there are <code>32</code> sessions started from <code>index == 0</code> appear twice, which means <code>42</code> sessions in total. Is this data error or intentional?<br>\nAnd the second question：<br>\nI think that's error data in the <code>elapsed_time</code></p>",
      "rawMarkdown": "I have the same question. For the first question:\nAccording to my observation, If this `index == 0` indicates that the session starts , there are `11769` sessions, but the unique `session_id` is `11779`, which means that at least `10` session not start from `index == 0`. And I also find there are `32` sessions started from `index == 0` appear twice, which means `42` sessions in total. Is this data error or intentional?\nAnd the second question：\nI think that's error data in the `elapsed_time `",
      "votes": null
    },
    {
      "id": "2134312",
      "postDate": "02/07/2023 22:15:21",
      "content": "<p>Thanks for highlighting this Quvotha and CxsGHost! Your understanding of the data is correct. These are both data errors in <code>elapsed_time</code> and <code>index</code>, which may be partly due to timestamps on the server sometimes being inaccurate if a student is clicking or performing other actions very quickly. You can assume that the <code>index</code> gives the correct order of events in cases where the <code>elapsed_time</code> is inconsistent. I'm less sure why the duplicates are occurring, but <code>index == 0</code> should indicate the start of a session and there should not be duplicate events for a session.</p>\n<p>The data could definitely be cleaner in this regard, but we also can expect some level of noise from collecting real-time game data. I hope that helps to clarify!</p>",
      "rawMarkdown": "Thanks for highlighting this Quvotha and CxsGHost! Your understanding of the data is correct. These are both data errors in `elapsed_time` and `index`, which may be partly due to timestamps on the server sometimes being inaccurate if a student is clicking or performing other actions very quickly. You can assume that the `index` gives the correct order of events in cases where the `elapsed_time` is inconsistent. I'm less sure why the duplicates are occurring, but `index == 0` should indicate the start of a session and there should not be duplicate events for a session.\n\nThe data could definitely be cleaner in this regard, but we also can expect some level of noise from collecting real-time game data. I hope that helps to clarify!",
      "votes": null
    },
    {
      "id": "2134521",
      "postDate": "02/08/2023 03:51:02",
      "content": "<p>Thank you Alex! Handling noise is difficult but interesting challenge.</p>",
      "rawMarkdown": "Thank you Alex! Handling noise is difficult but interesting challenge.",
      "votes": null
    },
    {
      "id": "2158164",
      "postDate": "02/24/2023 17:04:45",
      "content": "<p>Hi, thanks for clarifying this. Is this error also present in the test data?</p>",
      "rawMarkdown": "Hi, thanks for clarifying this. Is this error also present in the test data?",
      "votes": null
    }
  ],
  "comments": [
    {
      "id": 2133948,
      "author_name": "ghostcxs",
      "author_url": "",
      "post_date": "02/07/2023 17:22:32",
      "content": "<p>I have the same question. For the first question:<br>\nAccording to my observation, If this <code>index == 0</code> indicates that the session starts , there are <code>11769</code> sessions, but the unique <code>session_id</code> is <code>11779</code>, which means that at least <code>10</code> session not start from <code>index == 0</code>. And I also find there are <code>32</code> sessions started from <code>index == 0</code> appear twice, which means <code>42</code> sessions in total. Is this data error or intentional?<br>\nAnd the second question：<br>\nI think that's error data in the <code>elapsed_time</code></p>",
      "votes": null,
      "replies": []
    },
    {
      "id": 2134312,
      "author_name": "alexmlfranklin",
      "author_url": "",
      "post_date": "02/07/2023 22:15:21",
      "content": "<p>Thanks for highlighting this Quvotha and CxsGHost! Your understanding of the data is correct. These are both data errors in <code>elapsed_time</code> and <code>index</code>, which may be partly due to timestamps on the server sometimes being inaccurate if a student is clicking or performing other actions very quickly. You can assume that the <code>index</code> gives the correct order of events in cases where the <code>elapsed_time</code> is inconsistent. I'm less sure why the duplicates are occurring, but <code>index == 0</code> should indicate the start of a session and there should not be duplicate events for a session.</p>\n<p>The data could definitely be cleaner in this regard, but we also can expect some level of noise from collecting real-time game data. I hope that helps to clarify!</p>",
      "votes": null,
      "replies": [
        {
          "id": 2134521,
          "author_name": "tomokikmogura",
          "author_url": "",
          "post_date": "02/08/2023 03:51:02",
          "content": "<p>Thank you Alex! Handling noise is difficult but interesting challenge.</p>",
          "votes": null,
          "replies": []
        },
        {
          "id": 2158164,
          "author_name": "shashwatraman",
          "author_url": "",
          "post_date": "02/24/2023 17:04:45",
          "content": "<p>Hi, thanks for clarifying this. Is this error also present in the test data?</p>",
          "votes": null,
          "replies": []
        }
      ]
    }
  ],
  "raw_markdown_by_id": {
    "2133727": "In [Data tab](https://www.kaggle.com/competitions/predict-student-performance-from-game-play/data), `index` is explained as follows.\n\n> **index** - the index of the event for the session\n\nBut I have 2 questions about this column.\n\nFirst, I had assumed that each row in train.csv can be distinguished uniquely with `session_id` and `index`, but actually there are some duplication in \"train.csv\" (you can see that next Python code will return 17215 rows).\n\n```python\ndf = pd.read_csv(\"/kaggle/input/predict-student-performance-from-game-play/train.csv\", usecols=[\"session_id\", \"index\"])\ndf[df.duplicated(subset=[\"session_id\", \"index\"])]\n```\n\nIs this just a data bug or I misunderstood data definition?\n\nSecondly, I cannot understand the relation between `index` and `elapsed_time`. I had assumed that `index` represents event order in the session, but I found that `index` and `elapsed_time` orders are inconsistent in many `session_id`s.\n\nShortly, I cannot understand what this column represents! Could you please share your idea?",
    "2133948": "I have the same question. For the first question:\nAccording to my observation, If this `index == 0` indicates that the session starts , there are `11769` sessions, but the unique `session_id` is `11779`, which means that at least `10` session not start from `index == 0`. And I also find there are `32` sessions started from `index == 0` appear twice, which means `42` sessions in total. Is this data error or intentional?\nAnd the second question：\nI think that's error data in the `elapsed_time `",
    "2134312": "Thanks for highlighting this Quvotha and CxsGHost! Your understanding of the data is correct. These are both data errors in `elapsed_time` and `index`, which may be partly due to timestamps on the server sometimes being inaccurate if a student is clicking or performing other actions very quickly. You can assume that the `index` gives the correct order of events in cases where the `elapsed_time` is inconsistent. I'm less sure why the duplicates are occurring, but `index == 0` should indicate the start of a session and there should not be duplicate events for a session.\n\nThe data could definitely be cleaner in this regard, but we also can expect some level of noise from collecting real-time game data. I hope that helps to clarify!",
    "2134521": "Thank you Alex! Handling noise is difficult but interesting challenge.",
    "2158164": "Hi, thanks for clarifying this. Is this error also present in the test data?"
  },
  "source": "meta"
}