numpy_4 (incompleto).ipynb

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    "# Introdução ao Numpy - 4\n",
    "## Leonardo Yves de Souza Melo\n",
    "### (21)971771433 | prof.leoyves@gmail.com\n",
    "## Fontes:\n",
    "### 1) Python for Data Science Handbook - Jake VanderPlas; capítulo 2"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Bibliotecas"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [],
   "source": [
    "import numpy as np"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Indexação e partição de arrays\n",
    "\n",
    "Lembrando sempre que a contagem no python começa no índice 0"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [],
   "source": [
    "np.random.seed(42)\n",
    "x1 = np.random.randint(10,size=6)\n",
    "x2 = np.random.randint(10,size=(3,4))\n",
    "x3 = np.random.randint(10,size=(3,4,5))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([6, 3, 7, 4, 6, 9])"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    },
    {
     "data": {
      "text/plain": [
       "array([[2, 6, 7, 4],\n",
       "       [3, 7, 7, 2],\n",
       "       [5, 4, 1, 7]])"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    },
    {
     "data": {
      "text/plain": [
       "array([[[5, 1, 4, 0, 9],\n",
       "        [5, 8, 0, 9, 2],\n",
       "        [6, 3, 8, 2, 4],\n",
       "        [2, 6, 4, 8, 6]],\n",
       "\n",
       "       [[1, 3, 8, 1, 9],\n",
       "        [8, 9, 4, 1, 3],\n",
       "        [6, 7, 2, 0, 3],\n",
       "        [1, 7, 3, 1, 5]],\n",
       "\n",
       "       [[5, 9, 3, 5, 1],\n",
       "        [9, 1, 9, 3, 7],\n",
       "        [6, 8, 7, 4, 1],\n",
       "        [4, 7, 9, 8, 8]]])"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "display(x1,x2,x3)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [],
   "source": [
    "x = np.arange(10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "(array([0, 2, 4, 6, 8]), array([1, 3, 5, 7, 9]))"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# x[::2]   todos os elementos de índice par\n",
    "# x[1::2]  todos os elementos de índice ímpar\n",
    "x[::2],x[1::2]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "(array([9, 8, 7, 6, 5, 4, 3, 2, 1, 0]),\n",
       " array([9, 7, 5, 3, 1]),\n",
       " array([8, 6, 4, 2, 0]))"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# x[::-1]   todos os elementos na ordem reversa\n",
    "# x[::-2]   todos os elementos de índice par na ordem reversa\n",
    "# x[::-1][1::2]   todos os elementos de índice ímpar na ordem reversa\n",
    "x[::-1],x[::-2],x[::-1][1::2]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([5, 3, 1])"
      ]
     },
     "execution_count": 7,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# todos os elementos de índice par, considerando a partir do sexto elemento, na ordem reversa\n",
    "x[5::-2]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([[2, 6, 7],\n",
       "       [3, 7, 7]])"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# x2 é uma matriz 3x4\n",
    "## seleção das duas primeiras linhas e em cada linha, seleção dos três \n",
    "## primeiros elementos\n",
    "x2[:2,:3]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([[2, 7],\n",
       "       [3, 7],\n",
       "       [5, 1]])"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# seleção das três primeiras linhas\n",
    "# em cada linha seleção dos elementos de índice par\n",
    "x2[:3,::2]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([[99,  6],\n",
       "       [ 3,  7]])"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    },
    {
     "data": {
      "text/plain": [
       "array([[99,  6,  7,  4],\n",
       "       [ 3,  7,  7,  2],\n",
       "       [ 5,  4,  1,  7]])"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "# a alteração em x2_sub acarreta numa alteração em x2\n",
    "x2_sub = x2[:2,:2]\n",
    "x2_sub[0,0] = 99\n",
    "display(x2_sub,x2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([[42,  6],\n",
       "       [ 3,  7]])"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    },
    {
     "data": {
      "text/plain": [
       "array([[99,  6],\n",
       "       [ 3,  7]])"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    },
    {
     "data": {
      "text/plain": [
       "array([[99,  6,  7,  4],\n",
       "       [ 3,  7,  7,  2],\n",
       "       [ 5,  4,  1,  7]])"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "# a utilização do método copy criou um novo objeto fazendo com que a alteração\n",
    "# ficasse isolada\n",
    "x2_sub_copy = x2[:2,:2].copy()\n",
    "x2_sub_copy[0,0] = 42\n",
    "display(x2_sub_copy,x2_sub,x2)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([1, 2, 3])"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    },
    {
     "data": {
      "text/plain": [
       "array([3, 2, 1])"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    },
    {
     "data": {
      "text/plain": [
       "array([99, 99, 99])"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "x = np.arange(1,4)\n",
    "y = x[::-1].copy()\n",
    "z = np.ones_like(x)*99\n",
    "\n",
    "display(x,y,z)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([1, 2, 3, 3, 2, 1])"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    },
    {
     "data": {
      "text/plain": [
       "array([ 1,  2,  3,  3,  2,  1, 99, 99, 99])"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "# concatenação simples de dois ou mais arrays\n",
    "display(np.concatenate([x,y]),np.concatenate([x,y,z]))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([[1, 2, 3],\n",
       "       [4, 5, 6]])"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    },
    {
     "data": {
      "text/plain": [
       "array([[ 7,  8,  9],\n",
       "       [10, 11, 12]])"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "grid = np.arange(1,7).reshape(2,3)\n",
    "grid2 = np.arange(7,13).reshape(2,3)\n",
    "\n",
    "display(grid,grid2)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "``axis=0``: conexão de cada linha preservando as colunas.<br>\n",
    "``axis=1``: conexão de cada linha não preservando as colunas."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "(array([[ 1,  2,  3],\n",
       "        [ 4,  5,  6],\n",
       "        [ 7,  8,  9],\n",
       "        [10, 11, 12]]),\n",
       " array([[ 1,  2,  3,  7,  8,  9],\n",
       "        [ 4,  5,  6, 10, 11, 12]]))"
      ]
     },
     "execution_count": 15,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# concatenação simples de arrays multidimensionais\n",
    "# axis=0 é default argument\n",
    "np.concatenate([grid,grid2]),np.concatenate([grid,grid2],axis=1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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