numpy_lecture_3.ipynb

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   "outputs": [],
   "source": [
    "import numpy as np"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 13,
   "id": "66e5ab13-9ae3-4129-bf65-064496dfdeef",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([[ 0,  1,  2,  3],\n",
       "       [ 4,  5,  6,  7],\n",
       "       [ 8,  9, 10, 11],\n",
       "       [12, 13, 14, 15]])"
      ]
     },
     "execution_count": 13,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a = np.arange(16).reshape(4, 4)\n",
    "a"
   ]
  },
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   "cell_type": "code",
   "execution_count": 15,
   "id": "e23bca98-4c5f-47ad-9515-cfeabfd9e97f",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([0, 1, 2, 3])"
      ]
     },
     "execution_count": 15,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a[0] #first row"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "id": "2509229b-6bcd-4421-8bed-afb8afee1507",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([ 0,  4,  8, 12])"
      ]
     },
     "execution_count": 16,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a[:, 0] #first column"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 25,
   "id": "23c337d1-664e-49ef-8a44-214143d1b46a",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([[ 5,  6],\n",
       "       [ 9, 10]])"
      ]
     },
     "execution_count": 25,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a[1:3, 1:3] #middle 2x2 array"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 27,
   "id": "ddc73cd1-b490-438b-87ba-17b2e490f0b8",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([1, 5])"
      ]
     },
     "execution_count": 27,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a[(0,1), (1, 1)] #second element of first row and second element of second row"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 36,
   "id": "7e569747-2cda-401e-a9d2-c73fedd44d9c",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([[False,  True,  True,  True],\n",
       "       [ True,  True,  True,  True],\n",
       "       [ True,  True,  True,  True],\n",
       "       [ True,  True,  True,  True]])"
      ]
     },
     "execution_count": 36,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "idx = (a > 0)\n",
    "idx #Boolean matrix with same size as a"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 38,
   "id": "6d8cf88f-f27a-42ad-847b-375e2431ea8a",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([ 1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15])"
      ]
     },
     "execution_count": 38,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a[idx] #Creates a new array with matching values"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 41,
   "id": "afd39a5e-3879-42eb-8c1e-a47ab377f198",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "array([ 1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15])"
      ]
     },
     "execution_count": 41,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "a[a > 0] #same with above"
   ]
  }
 ],
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