{
  "cells": [
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "![Impressions](https://PixelServer20190423114238.azurewebsites.net/api/impressions/MachineLearningNotebooks/work-with-data/dataprep/how-to-guides/random-split.png)"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "# Random Split\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {},
      "outputs": [],
      "source": [
        "import azureml.dataprep as dprep"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Azure ML Data Prep provides the functionality of splitting a data set into two. When training a machine learning model, it is often desirable to train the model on a subset of data, then validate the model on a different subset."
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "The `random_split(percentage, seed=None)` function in Data Prep takes in a Dataflow and randomly splitting it into two distinct subsets (approximately by the percentage specified)."
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "The `seed` parameter is optional. If a seed is not provided, a stable one is generated, ensuring that the results for a specific Dataflow remain consistent. Different calls to `random_split` will receive different seeds."
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "To demonstrate, you can go through the following example. First, you can read the first 10,000 lines from a file. Since the contents of the file don't matter, just the first two columns can be used for a simple example."
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {},
      "outputs": [],
      "source": [
        "dflow = dprep.read_csv(path='https://dpreptestfiles.blob.core.windows.net/testfiles/crime0.csv').take(10000)\n",
        "dflow = dflow.keep_columns(['ID', 'Date'])\n",
        "profile = dflow.get_profile()\n",
        "print('Row count: %d' % (profile.columns['ID'].count))"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Next, you can call `random_split` with the percentage set to 10% (the actual split ratio will be an approximation of `percentage`). You can take a look at the row count of the first returned Dataflow. You should see that `dflow_test` has approximately 1,000 rows (10% of 10,000)."
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {},
      "outputs": [],
      "source": [
        "(dflow_test, dflow_train) = dflow.random_split(percentage=0.1)\n",
        "profile_test = dflow_test.get_profile()\n",
        "print('Row count of \"test\": %d' % (profile_test.columns['ID'].count))"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Now you can take a look at the row count of the second returned Dataflow. The row count of `dflow_test` and `dflow_train` sums exactly to 10,000, because `random_split` results in two subsets that make up the original Dataflow."
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {},
      "outputs": [],
      "source": [
        "profile_train = dflow_train.get_profile()\n",
        "print('Row count of \"train\": %d' % (profile_train.columns['ID'].count))"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "To specify a fixed seed, simply provide it to the `random_split` function."
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {},
      "outputs": [],
      "source": [
        "(dflow_test, dflow_train) = dflow.random_split(percentage=0.1, seed=12345)"
      ]
    }
  ],
  "metadata": {
    "authors": [
      {
        "name": "sihhu"
      }
    ],
    "kernelspec": {
      "display_name": "Python 3.6",
      "language": "python",
      "name": "python36"
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      "file_extension": ".py",
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      "name": "python",
      "nbconvert_exporter": "python",
      "pygments_lexer": "ipython3",
      "version": "3.6.4"
    },
    "notice": "Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT License."
  },
  "nbformat": 4,
  "nbformat_minor": 2
}