numpy_indices.ipynb

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      "source": [
        "https://numpy.org/doc/stable/reference/generated/numpy.indices.html"
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      "execution_count": 2,
      "metadata": {
        "id": "G0XF8XZLjVQu"
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      "source": [
        "import numpy as np"
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "grid = np.indices((2, 3))"
      ],
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        "id": "Rz8N845Klr6i"
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      "outputs": []
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        "grid.shape"
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              "(2, 2, 3)"
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              "array([[[0, 0, 0],\n",
              "        [1, 1, 1]],\n",
              "\n",
              "       [[0, 1, 2],\n",
              "        [0, 1, 2]]])"
            ]
          },
          "metadata": {},
          "execution_count": 5
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "x = np.arange(20).reshape(5, 4)"
      ],
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            "text/plain": [
              "array([[ 0,  1,  2,  3],\n",
              "       [ 4,  5,  6,  7],\n",
              "       [ 8,  9, 10, 11],\n",
              "       [12, 13, 14, 15],\n",
              "       [16, 17, 18, 19]])"
            ]
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          "metadata": {},
          "execution_count": 7
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    {
      "cell_type": "code",
      "source": [
        "row, col = np.indices((2, 3))"
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        "id": "hcapar5-lsJc"
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              "array([[0, 0, 0],\n",
              "       [1, 1, 1]])"
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          "execution_count": 9
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              "array([[0, 1, 2],\n",
              "       [4, 5, 6]])"
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          "execution_count": 11
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        "x[:2, :3]"
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        ""
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        "i, j = np.indices((2, 3), sparse=True)"
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      "outputs": []
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        "i"
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            "text/plain": [
              "array([[0],\n",
              "       [1]])"
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          "execution_count": 14
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      "execution_count": 15,
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        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0, 1, 2]])"
            ]
          },
          "metadata": {},
          "execution_count": 15
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        ""
      ],
      "metadata": {
        "id": "jv9HiTg3miPy"
      },
      "execution_count": 15,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "i, j = np.indices((2, 3))"
      ],
      "metadata": {
        "id": "Lp5JTVnWGSR0"
      },
      "execution_count": 16,
      "outputs": []
    },
    {
      "cell_type": "code",
      "source": [
        "i"
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        "outputId": "4b412b2c-3143-4b6b-e4f1-b5d070f4d820"
      },
      "execution_count": 17,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0, 0, 0],\n",
              "       [1, 1, 1]])"
            ]
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          "metadata": {},
          "execution_count": 17
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      "execution_count": 18,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[0, 1, 2],\n",
              "       [0, 1, 2]])"
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          "metadata": {},
          "execution_count": 18
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      "cell_type": "code",
      "source": [
        ""
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      "metadata": {
        "id": "NqQKBGPmGSbb"
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      "execution_count": 18,
      "outputs": []
    },
    {
      "cell_type": "markdown",
      "source": [
        "## Test with a sample matrix"
      ],
      "metadata": {
        "id": "x8l06G_gmiSd"
      }
    },
    {
      "cell_type": "code",
      "source": [
        "idx_test = np.indices((2,3))\n",
        "idx_test"
      ],
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          "base_uri": "https://localhost:8080/"
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        "id": "0urIaRh44ss_",
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        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "array([[[0, 0, 0],\n",
              "        [1, 1, 1]],\n",
              "\n",
              "       [[0, 1, 2],\n",
              "        [0, 1, 2]]])"
            ]
          },
          "metadata": {},
          "execution_count": 45
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "idx_test.shape"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "kyLJ6FQmEjzz",
        "outputId": "437e4bef-a5f7-4361-83ff-a6376c4dc844"
      },
      "execution_count": null,
      "outputs": [
        {
          "output_type": "execute_result",
          "data": {
            "text/plain": [
              "(2, 2, 3)"
            ]
          },
          "metadata": {},
          "execution_count": 46
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "idx_test2 = np.indices((2,3,4))\n",
        "idx_test2"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "aOU3fEEDEj2l",
        "outputId": "596f71b8-2ff3-4893-e43f-0b10fdeec414"
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      "execution_count": null,
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        {
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              "array([[[[0, 0, 0, 0],\n",
              "         [0, 0, 0, 0],\n",
              "         [0, 0, 0, 0]],\n",
              "\n",
              "        [[1, 1, 1, 1],\n",
              "         [1, 1, 1, 1],\n",
              "         [1, 1, 1, 1]]],\n",
              "\n",
              "\n",
              "       [[[0, 0, 0, 0],\n",
              "         [1, 1, 1, 1],\n",
              "         [2, 2, 2, 2]],\n",
              "\n",
              "        [[0, 0, 0, 0],\n",
              "         [1, 1, 1, 1],\n",
              "         [2, 2, 2, 2]]],\n",
              "\n",
              "\n",
              "       [[[0, 1, 2, 3],\n",
              "         [0, 1, 2, 3],\n",
              "         [0, 1, 2, 3]],\n",
              "\n",
              "        [[0, 1, 2, 3],\n",
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              "         [0, 1, 2, 3]]]])"
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        "idx_test2.shape"
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              "(3, 2, 3, 4)"
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          "metadata": {},
          "execution_count": 48
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        ""
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        "id": "9F-1jtd8Ej77"
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        "idx_test2"
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        "id": "V8yDerkOEj-0",
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              "array([[[[0, 0, 0, 0],\n",
              "         [0, 0, 0, 0],\n",
              "         [0, 0, 0, 0]],\n",
              "\n",
              "        [[1, 1, 1, 1],\n",
              "         [1, 1, 1, 1],\n",
              "         [1, 1, 1, 1]]],\n",
              "\n",
              "\n",
              "       [[[0, 0, 0, 0],\n",
              "         [1, 1, 1, 1],\n",
              "         [2, 2, 2, 2]],\n",
              "\n",
              "        [[0, 0, 0, 0],\n",
              "         [1, 1, 1, 1],\n",
              "         [2, 2, 2, 2]]],\n",
              "\n",
              "\n",
              "       [[[0, 1, 2, 3],\n",
              "         [0, 1, 2, 3],\n",
              "         [0, 1, 2, 3]],\n",
              "\n",
              "        [[0, 1, 2, 3],\n",
              "         [0, 1, 2, 3],\n",
              "         [0, 1, 2, 3]]]])"
            ]
          },
          "metadata": {},
          "execution_count": 49
        }
      ]
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    {
      "cell_type": "code",
      "source": [
        "idx_test2.ravel(order='C')"
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        "id": "wR-nzUAOEkCA",
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            "text/plain": [
              "array([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,\n",
              "       1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 0, 0, 0, 0, 1, 1, 1, 1,\n",
              "       2, 2, 2, 2, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1, 2, 3, 0, 1,\n",
              "       2, 3, 0, 1, 2, 3])"
            ]
          },
          "metadata": {},
          "execution_count": 50
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        "idx_test2"
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        "outputId": "05ec3f33-5f35-4e50-da66-79085369c39c"
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            "text/plain": [
              "array([[[[0, 0, 0, 0],\n",
              "         [0, 0, 0, 0],\n",
              "         [0, 0, 0, 0]],\n",
              "\n",
              "        [[1, 1, 1, 1],\n",
              "         [1, 1, 1, 1],\n",
              "         [1, 1, 1, 1]]],\n",
              "\n",
              "\n",
              "       [[[0, 0, 0, 0],\n",
              "         [1, 1, 1, 1],\n",
              "         [2, 2, 2, 2]],\n",
              "\n",
              "        [[0, 0, 0, 0],\n",
              "         [1, 1, 1, 1],\n",
              "         [2, 2, 2, 2]]],\n",
              "\n",
              "\n",
              "       [[[0, 1, 2, 3],\n",
              "         [0, 1, 2, 3],\n",
              "         [0, 1, 2, 3]],\n",
              "\n",
              "        [[0, 1, 2, 3],\n",
              "         [0, 1, 2, 3],\n",
              "         [0, 1, 2, 3]]]])"
            ]
          },
          "metadata": {},
          "execution_count": 51
        }
      ]
    },
    {
      "cell_type": "code",
      "source": [
        "idx_test2.ravel(order='F')"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
        },
        "id": "AkmlO4ze4s6J",
        "outputId": "96a02342-a3ac-4862-df6c-7441191d4ced"
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      "execution_count": null,
      "outputs": [
        {
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          "data": {
            "text/plain": [
              "array([0, 0, 0, 1, 0, 0, 0, 1, 0, 1, 1, 0, 0, 2, 0, 1, 2, 0, 0, 0, 1, 1,\n",
              "       0, 1, 0, 1, 1, 1, 1, 1, 0, 2, 1, 1, 2, 1, 0, 0, 2, 1, 0, 2, 0, 1,\n",
              "       2, 1, 1, 2, 0, 2, 2, 1, 2, 2, 0, 0, 3, 1, 0, 3, 0, 1, 3, 1, 1, 3,\n",
              "       0, 2, 3, 1, 2, 3])"
            ]
          },
          "metadata": {},
          "execution_count": 52
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      "source": [
        ""
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      "execution_count": null,
      "outputs": []
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    {
      "cell_type": "code",
      "source": [
        "idx_test2_sparse = np.indices((2,3,4), sparse=True)\n",
        "idx_test2_sparse"
      ],
      "metadata": {
        "colab": {
          "base_uri": "https://localhost:8080/"
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        "id": "9jIshnZ4PZgz",
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            "text/plain": [
              "(array([[[0]],\n",
              " \n",
              "        [[1]]]), array([[[0],\n",
              "         [1],\n",
              "         [2]]]), array([[[0, 1, 2, 3]]]))"
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          "metadata": {},
          "execution_count": 53
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        "id": "vidnPEXqmiVF"
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      "execution_count": 18,
      "outputs": []
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}