33 Regular Expressions.ipynb

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   "source": [
    "# Regular Expressions"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Regular expressions is a general term which covers the idea of pattern searching, typically in a string (or a vector of strings).\n",
    "\n",
    "For now we'll learn about two useful functions for regular expressions and pattern searching (we'll go deeper into this topic in general later on):\n",
    "\n",
    "- __grepl()__: Returns a logical indicating if the pattern was found\n",
    "\n",
    "- __grep()__: Returns a vector of index locations of matching pattern instances\n",
    "\n",
    "For both of these functions you'll pass in a pattern and then the object you want to search. Let's see some quick examples:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 18,
   "metadata": {},
   "outputs": [],
   "source": [
    "text <- \"Hi there! do you know who you're voting for?\""
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 21,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "TRUE"
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      "text/latex": [
       "TRUE"
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       "TRUE"
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      "text/plain": [
       "[1] TRUE"
      ]
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       "FALSE"
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      "text/plain": [
       "[1] FALSE"
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       "[1] TRUE"
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   "source": [
    "grepl('voting',text)\n",
    "grepl('dog',text)\n",
    "grepl('do you know',text)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<style>\n",
       ".list-inline {list-style: none; margin:0; padding: 0}\n",
       ".list-inline>li {display: inline-block}\n",
       ".list-inline>li:not(:last-child)::after {content: \"\\00b7\"; padding: 0 .5ex}\n",
       "</style>\n",
       "<ol class=list-inline><li>'a'</li><li>'b'</li><li>'c'</li><li>'d'</li><li>'d'</li></ol>\n"
      ],
      "text/latex": [
       "\\begin{enumerate*}\n",
       "\\item 'a'\n",
       "\\item 'b'\n",
       "\\item 'c'\n",
       "\\item 'd'\n",
       "\\item 'd'\n",
       "\\end{enumerate*}\n"
      ],
      "text/markdown": [
       "1. 'a'\n",
       "2. 'b'\n",
       "3. 'c'\n",
       "4. 'd'\n",
       "5. 'd'\n",
       "\n",
       "\n"
      ],
      "text/plain": [
       "[1] \"a\" \"b\" \"c\" \"d\" \"d\""
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "v <- c('a','b','c','d','d')\n",
    "v"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 15,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<style>\n",
       ".list-inline {list-style: none; margin:0; padding: 0}\n",
       ".list-inline>li {display: inline-block}\n",
       ".list-inline>li:not(:last-child)::after {content: \"\\00b7\"; padding: 0 .5ex}\n",
       "</style>\n",
       "<ol class=list-inline><li>FALSE</li><li>TRUE</li><li>FALSE</li><li>FALSE</li><li>FALSE</li></ol>\n"
      ],
      "text/latex": [
       "\\begin{enumerate*}\n",
       "\\item FALSE\n",
       "\\item TRUE\n",
       "\\item FALSE\n",
       "\\item FALSE\n",
       "\\item FALSE\n",
       "\\end{enumerate*}\n"
      ],
      "text/markdown": [
       "1. FALSE\n",
       "2. TRUE\n",
       "3. FALSE\n",
       "4. FALSE\n",
       "5. FALSE\n",
       "\n",
       "\n"
      ],
      "text/plain": [
       "[1] FALSE  TRUE FALSE FALSE FALSE"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "grepl('b',v)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 16,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "2"
      ],
      "text/latex": [
       "2"
      ],
      "text/markdown": [
       "2"
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      "text/plain": [
       "[1] 2"
      ]
     },
     "metadata": {},
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   ],
   "source": [
    "grep('b',v)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 17,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/html": [
       "<style>\n",
       ".list-inline {list-style: none; margin:0; padding: 0}\n",
       ".list-inline>li {display: inline-block}\n",
       ".list-inline>li:not(:last-child)::after {content: \"\\00b7\"; padding: 0 .5ex}\n",
       "</style>\n",
       "<ol class=list-inline><li>4</li><li>5</li></ol>\n"
      ],
      "text/latex": [
       "\\begin{enumerate*}\n",
       "\\item 4\n",
       "\\item 5\n",
       "\\end{enumerate*}\n"
      ],
      "text/markdown": [
       "1. 4\n",
       "2. 5\n",
       "\n",
       "\n"
      ],
      "text/plain": [
       "[1] 4 5"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "grep('d',v)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "[Good sources](http://www.regular-expressions.info/rlanguage.html)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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