{
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   "source": [
    "<!--- Licensed to the Apache Software Foundation (ASF) under one -->\n",
    "<!--- or more contributor license agreements.  See the NOTICE file -->\n",
    "<!--- distributed with this work for additional information -->\n",
    "<!--- regarding copyright ownership.  The ASF licenses this file -->\n",
    "<!--- to you under the Apache License, Version 2.0 (the -->\n",
    "<!--- \"License\"); you may not use this file except in compliance -->\n",
    "<!--- with the License.  You may obtain a copy of the License at -->\n",
    "\n",
    "<!---   http://www.apache.org/licenses/LICENSE-2.0 -->\n",
    "\n",
    "<!--- Unless required by applicable law or agreed to in writing, -->\n",
    "<!--- software distributed under the License is distributed on an -->\n",
    "<!--- \"AS IS\" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY -->\n",
    "<!--- KIND, either express or implied.  See the License for the -->\n",
    "<!--- specific language governing permissions and limitations -->\n",
    "<!--- under the License. -->\n",
    "\n",
    "# Manipulate data with `ndarray`\n",
    "\n",
    "We'll start by introducing the `NDArray`, MXNet’s primary tool for storing and transforming data. If you’ve worked with `NumPy` before, you’ll notice that an NDArray is, by design, similar to NumPy’s multi-dimensional array.\n",
    "\n",
    "## Get started\n",
    "\n",
    "To get started, let's import the `ndarray` package (`nd` is a shorter alias) from MXNet."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
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     "n": "1"
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   },
   "outputs": [],
   "source": [
    "# If you haven't installed MXNet yet, you can uncomment the following line to\n",
    "# install the latest stable release\n",
    "# !pip install -U mxnet\n",
    "\n",
    "from mxnet import nd"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Next, let's see how to create a 2D array (also called a matrix) with values from two sets of numbers: 1, 2, 3 and 4, 5, 6. This might also be referred to as a tuple of a tuple of integers."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "attributes": {
     "classes": [],
     "id": "",
     "n": "2"
    }
   },
   "outputs": [],
   "source": [
    "nd.array(((1,2,3),(5,6,7)))"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "We can also create a very simple matrix with the same shape (2 rows by 3 columns), but fill it with 1s."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "attributes": {
     "classes": [],
     "id": "",
     "n": "3"
    }
   },
   "outputs": [],
   "source": [
    "x = nd.ones((2,3))\n",
    "x"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Often we’ll want to create arrays whose values are sampled randomly. For example, sampling values uniformly between -1 and 1. Here we create the same shape, but with random sampling."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {
    "attributes": {
     "classes": [],
     "id": "",
     "n": "15"
    }
   },
   "outputs": [],
   "source": [
    "y = nd.random.uniform(-1,1,(2,3))\n",
    "y"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "You can also fill an array of a given shape with a given value, such as `2.0`.\n",
    "<!-- added to improve multiplication example -->"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {
    "attributes": {
     "classes": [],
     "id": "",
     "n": "16"
    }
   },
   "outputs": [],
   "source": [
    "x = nd.full((2,3), 2.0)\n",
    "x"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "As with NumPy, the dimensions of each NDArray are accessible by accessing the `.shape` attribute. We can also query its `size`, which is equal to the product of the components of the shape. In addition, `.dtype` tells the data type of the stored values."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {
    "attributes": {
     "classes": [],
     "id": "",
     "n": "17"
    }
   },
   "outputs": [],
   "source": [
    "(x.shape, x.size, x.dtype)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Operations\n",
    "\n",
    "NDArray supports a large number of standard mathematical operations, such as element-wise multiplication:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {
    "attributes": {
     "classes": [],
     "id": "",
     "n": "18"
    }
   },
   "outputs": [],
   "source": [
    "x * y"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Exponentiation:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "metadata": {
    "attributes": {
     "classes": [],
     "id": "",
     "n": "23"
    }
   },
   "outputs": [],
   "source": [
    "y.exp()"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "And transposing a matrix to compute a proper matrix-matrix product:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 24,
   "metadata": {
    "attributes": {
     "classes": [],
     "id": "",
     "n": "24"
    }
   },
   "outputs": [],
   "source": [
    "nd.dot(x, y.T)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Indexing\n",
    "\n",
    "MXNet NDArrays support slicing in all the ridiculous ways you might imagine accessing your data. Here’s an example of reading a particular element, which returns a 1D array with shape `(1,)`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "metadata": {
    "attributes": {
     "classes": [],
     "id": "",
     "n": "25"
    }
   },
   "outputs": [],
   "source": [
    "y[1,2]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Read the second and third columns from `y`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 26,
   "metadata": {
    "attributes": {
     "classes": [],
     "id": "",
     "n": "26"
    }
   },
   "outputs": [],
   "source": [
    "y[:,1:3]"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "and write to a specific element."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 27,
   "metadata": {
    "attributes": {
     "classes": [],
     "id": "",
     "n": "27"
    }
   },
   "outputs": [],
   "source": [
    "y[:,1:3] = 2\n",
    "y"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Multi-dimensional slicing is also supported."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 28,
   "metadata": {
    "attributes": {
     "classes": [],
     "id": "",
     "n": "28"
    }
   },
   "outputs": [],
   "source": [
    "y[1:2,0:2] = 4\n",
    "y"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Converting between MXNet NDArray and NumPy\n",
    "\n",
    "Converting MXNet NDArrays to and from NumPy is easy. The converted arrays do not share memory."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 29,
   "metadata": {
    "attributes": {
     "classes": [],
     "id": "",
     "n": "29"
    }
   },
   "outputs": [],
   "source": [
    "a = x.asnumpy()\n",
    "(type(a), a)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 30,
   "metadata": {
    "attributes": {
     "classes": [],
     "id": "",
     "n": "30"
    }
   },
   "outputs": [],
   "source": [
    "nd.array(a)"
   ]
  }
 ],
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