3장_넘파이_배열_프로그래밍_(3.4&5).ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "id": "5fdc8fde",
   "metadata": {},
   "source": [
    "# 기술 통계"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "33cb38a5",
   "metadata": {},
   "source": [
    "넘파이는 다음과 같은 데이터 집합에 대해 간단한 통계를 계산하는 함수를 제공한다. 이러한 값들을 통틀어 기술 통계(descriptive statistics)라고 한다.\n",
    "\n",
    "* 데이터의 개수(count)\n",
    "\n",
    "* 평균(mean, average)\n",
    "\n",
    "* 분산(variance)\n",
    "\n",
    "* 표준 편차(standard deviation)\n",
    "\n",
    "* 최댓값(maximum)\n",
    "\n",
    "* 최솟값(minimum)\n",
    "\n",
    "* 중앙값(median)\n",
    "\n",
    "* 사분위수(quartile)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "06a73ca9",
   "metadata": {},
   "outputs": [],
   "source": [
    "import numpy as np\n",
    "\n",
    "x = np.array([18,   5,  10,  23,  19,  -8,  10,   0,   0,   5,   2,  15,   8,\n",
    "              2,   5,   4,  15,  -1,   4,  -7, -24,   7,   9,  -6,  23, -13])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "a13ec7b4",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "26"
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "len(x)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "id": "0cb163da",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "4.8076923076923075"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.mean(x)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "id": "6db1e378",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "119.84153846153846"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.var(x, ddof = 1)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "id": "235e2e38",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "10.734628476137871"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.std(x)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "id": "b9d90d72",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "23"
      ]
     },
     "execution_count": 10,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.max(x)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "id": "860d01ae",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "-24"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.min(x)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "id": "726c4c36",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "5.0"
      ]
     },
     "execution_count": 12,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.median(x)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "id": "1ebbcd7b",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "-24.0"
      ]
     },
     "execution_count": 13,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.percentile(x, 0)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 14,
   "id": "0088f732",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "0.0"
      ]
     },
     "execution_count": 14,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.percentile(x, 25)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "id": "2b51a4fb",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "5.0"
      ]
     },
     "execution_count": 15,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.percentile(x, 50)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "id": "e9dc2dda",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "10.0"
      ]
     },
     "execution_count": 16,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.percentile(x, 75)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "id": "9663657d",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "23.0"
      ]
     },
     "execution_count": 17,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.percentile(x, 100)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "8e724bd4",
   "metadata": {},
   "source": [
    "# 난수 발생과 카운팅"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 22,
   "id": "9e2f928b",
   "metadata": {},
   "outputs": [],
   "source": [
    "np.random.seed(42)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 23,
   "id": "ce0f046b",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([0.37454012, 0.95071431, 0.73199394, 0.59865848, 0.15601864])"
      ]
     },
     "execution_count": 23,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.rand(5)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 24,
   "id": "a0e0b542",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([0.15599452, 0.05808361, 0.86617615, 0.60111501, 0.70807258,\n",
       "       0.02058449, 0.96990985, 0.83244264, 0.21233911, 0.18182497])"
      ]
     },
     "execution_count": 24,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.rand(10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "id": "f36ff84d",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([0.18340451, 0.30424224, 0.52475643, 0.43194502, 0.29122914,\n",
       "       0.61185289, 0.13949386, 0.29214465, 0.36636184, 0.45606998])"
      ]
     },
     "execution_count": 25,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.rand(10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 26,
   "id": "e8a53800",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([0.78517596, 0.19967378, 0.51423444, 0.59241457, 0.04645041,\n",
       "       0.60754485, 0.17052412, 0.06505159, 0.94888554, 0.96563203])"
      ]
     },
     "execution_count": 26,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.rand(10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 27,
   "id": "bb2c44aa",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([0.80839735, 0.30461377, 0.09767211, 0.68423303, 0.44015249])"
      ]
     },
     "execution_count": 27,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.rand(5)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 28,
   "id": "29bfe175",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([0.37454012, 0.95071431, 0.73199394, 0.59865848, 0.15601864])"
      ]
     },
     "execution_count": 28,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.seed(42)\n",
    "np.random.rand(5)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 29,
   "id": "a0a96e42",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])"
      ]
     },
     "execution_count": 29,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "x = np.arange(10)\n",
    "x"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 32,
   "id": "0ebc660c",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([2, 8, 0, 7, 6, 4, 5, 9, 1, 3])"
      ]
     },
     "execution_count": 32,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.shuffle(x)\n",
    "x"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "e830be1f",
   "metadata": {},
   "source": [
    "numpy.random.choice(a, size=None, replace=True, p=None)\n",
    "\n",
    "* a : 배열이면 원래의 데이터, 정수이면 arange(a) 명령으로 데이터 생성\n",
    "\n",
    "* size : 정수. 샘플 숫자\n",
    "\n",
    "* replace : 불리언. True이면 한번 선택한 데이터를 다시 선택 가능\n",
    "\n",
    "* p : 배열. 각 데이터가 선택될 수 있는 확률"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 33,
   "id": "86fc8323",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([2, 0, 4, 1, 3])"
      ]
     },
     "execution_count": 33,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.choice(5, 5, replace=False)  # shuffle 명령과 같다."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 34,
   "id": "5087d4f5",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([1, 2, 4])"
      ]
     },
     "execution_count": 34,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.choice(5, 3, replace=False)  # 3개만 선택"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 40,
   "id": "f1db5cb1",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([0, 2, 3])"
      ]
     },
     "execution_count": 40,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.choice(5, 3, p=[0.9, 0.025, 0.025, 0.025, 0.025])"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "6be2448a",
   "metadata": {},
   "source": [
    "넘파이의 random 서브패키지는 이외에도 난수를 생성하는 다양한 함수를 제공한다. 그 중 가장 간단하고 많이 사용되는 것은 다음 3가지 함수다.\n",
    "\n",
    "* rand: 0부터 1사이의 균일 분포\n",
    "\n",
    "* randn: 표준 정규 분포\n",
    "\n",
    "* randint: 균일 분포의 정수 난수"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 41,
   "id": "d69e0152",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([0.80839735, 0.30461377, 0.09767211, 0.68423303, 0.44015249,\n",
       "       0.12203823, 0.49517691, 0.03438852, 0.9093204 , 0.25877998])"
      ]
     },
     "execution_count": 41,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.rand(10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 42,
   "id": "2243b849",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([[0.66252228, 0.31171108, 0.52006802, 0.54671028, 0.18485446],\n",
       "       [0.96958463, 0.77513282, 0.93949894, 0.89482735, 0.59789998],\n",
       "       [0.92187424, 0.0884925 , 0.19598286, 0.04522729, 0.32533033]])"
      ]
     },
     "execution_count": 42,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.rand(3, 5)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 43,
   "id": "763eb308",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([-1.47852199, -0.71984421, -0.46063877,  1.05712223,  0.34361829,\n",
       "       -1.76304016,  0.32408397, -0.38508228, -0.676922  ,  0.61167629])"
      ]
     },
     "execution_count": 43,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.randn(10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 44,
   "id": "13caa9a6",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([[ 1.03099952,  0.93128012, -0.83921752, -0.30921238,  0.33126343],\n",
       "       [ 0.97554513, -0.47917424, -0.18565898, -1.10633497, -1.19620662],\n",
       "       [ 0.81252582,  1.35624003, -0.07201012,  1.0035329 ,  0.36163603]])"
      ]
     },
     "execution_count": 44,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.randn(3, 5)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 45,
   "id": "43190c13",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([0, 4, 9, 6, 6, 8, 9, 9, 2, 6])"
      ]
     },
     "execution_count": 45,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.randint(10, size=10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 46,
   "id": "d134bc27",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([[10, 13, 13, 14, 16],\n",
       "       [16, 13, 16, 12, 15],\n",
       "       [11, 19, 18, 14, 15]])"
      ]
     },
     "execution_count": 46,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.randint(10, 20, size=(3, 5))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 52,
   "id": "d09e9e45",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([1, 1, 0, 1, 0, 0, 0, 0, 1, 0])"
      ]
     },
     "execution_count": 52,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.random.randint(0, 2, size = 10)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 54,
   "id": "cf11dc33",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([1, 2, 3, 4, 5, 6])"
      ]
     },
     "execution_count": 54,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "x = np.arange(1,7)\n",
    "x"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 61,
   "id": "c0be0564",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "3.33"
      ]
     },
     "execution_count": 61,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "dice = []\n",
    "for i in range(100):\n",
    "    dice.append(np.random.choice(np.arange(1,7),1))\n",
    "np.mean(dice)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 67,
   "id": "ac9f8ca2",
   "metadata": {},
   "outputs": [],
   "source": [
    "stock = 10000\n",
    "stock_date = []\n",
    "for i in range(250):\n",
    "    stock = stock * np.random.randn()\n",
    "    stock_date.append(stock)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 68,
   "id": "a11b1cfe",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([ 2, 11, 34])"
      ]
     },
     "execution_count": 68,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "np.unique([11, 11, 2, 2, 34, 34])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 69,
   "id": "89d74ebe",
   "metadata": {},
   "outputs": [],
   "source": [
    "a = np.array(['a', 'b', 'b', 'c', 'a'])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 70,
   "id": "b4d9a7e9",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array(['a', 'b', 'b', 'c', 'a'], dtype='<U1')"
      ]
     },
     "execution_count": 70,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 72,
   "id": "0dba03b4",
   "metadata": {},
   "outputs": [],
   "source": [
    "index, count = np.unique(a, return_counts = True)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 73,
   "id": "1d070447",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array(['a', 'b', 'c'], dtype='<U1')"
      ]
     },
     "execution_count": 73,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "index"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 74,
   "id": "1b199403",
   "metadata": {},
   "outputs": [
    {
     "data": {
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