{"id":905,"date":"2019-02-20T18:58:48","date_gmt":"2019-02-20T09:58:48","guid":{"rendered":"http:\/\/141.164.34.82\/?p=905"},"modified":"2019-08-04T15:27:17","modified_gmt":"2019-08-04T06:27:17","slug":"xx-useless-equation","status":"publish","type":"post","link":"http:\/\/ds.sumeun.org\/?p=905","title":{"rendered":"x==x; Useless Equation?"},"content":{"rendered":"<h1>\uc0c8\ucc45 \uc18c\uac1c (R\ub85c \ud558\ub294 \ube45\ub370\uc774\ud130 \ubd84\uc11d)[<sup>1]<\/sup><\/h1>\n<ul>\n<li>\uc81c\ubaa9 : <a href=\"http:\/\/141.164.34.82\/?p=891\">R\ub85c \ud558\ub294 \ube45\ub370\uc774\ud130 \ubd84\uc11d: \ub370\uc774\ud130 \uc804\ucc98\ub9ac\uc640 \uc2dc\uac01\ud654<\/a><\/li>\n<li>\ucd9c\ud310\uc0ac : \uc228\uc740\uc6d0\ub9ac<\/li>\n<li>\uc9c0\uc74c : \uae40\uad8c\ud604 <\/li>\n<li>\ucabd\uc218 : 328\ucabd <\/li>\n<li>\ubc1c\ud589\uc77c : 2019\ub144 3\uc6d4 1\uc77c <\/li>\n<li>ISBN : 979-11-960144-7-6(93000)<\/li>\n<li>\uc774 \ud3ec\uc2a4\ud2b8\uc758 \uc8fc\uc18c : <a href=\"http:\/\/141.164.34.82\/?p=905\">http:\/\/141.164.34.82\/?p=905<\/a><\/li>\n<\/ul>\n<p>[<sup>1]:<\/sup> \uc774 \ud3ec\uc2a4\ud2b8(post)\ub294 2019\ub144 2\uc6d4 20\uc77c \ubc1c\ud45c \ub0b4\uc6a9\uc785\ub2c8\ub2e4. <\/p>\n<h2>\uc9c0\uc740\uc774 \uc18c\uac1c<\/h2>\n<ul>\n<li>\uc774\ub984 : \uae40\uad8c\ud604<\/li>\n<li>\uc11c\uc6b8\ub300 \uc778\uc9c0\uacfc\ud559 \ubc15\uc0ac<\/li>\n<li>\uc11c\uac15\ub300, \uad6d\ubbfc\ub300, \uba85\uc9c0\ub300 \ub4f1 \ucd9c\uac15<\/li>\n<li>\uc9c0\ub09c\ud574 <code>zeroone.ai<\/code> AI Research Lead<\/li>\n<li>\uc804\uc791\n<ul>\n<li><a href=\"https:\/\/www.aladin.co.kr\/shop\/wproduct.aspx?ItemId=32237840\">\uae30\ucd08 \ud1b5\uacc4\ud559\uc758 \uc228\uc740 \uc6d0\ub9ac \uc774\ud574\ud558\uae30<\/a><\/li>\n<li><a href=\"https:\/\/buk.io\/@ka6911\/11\">\uc218\ud559\uc758 \uc228\uc740 \uc6d0\ub9ac<\/a><\/li>\n<li><a href=\"http:\/\/books.sumeun.org\/index.php\/2019\/01\/04\/highschoolfactoring\/\">\uace0\ub4f1\ud559\uad50 \uc778\uc218\ubd84\ud574 (\uac70\uc758) \uc644\uc804 \uc815\ubcf5<\/a><\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h2>\ucc45\uc744 \uc4f0\uac8c \ub41c \ub3d9\uae30<\/h2>\n<p>\uc6b0\uc120 R\uc758 \ubcf5\uc7a1\ud55c \uad6c\ubb38\uc744 \ud55c\ubc88 \uc0b4\ud3b4 \ubd05\uc2dc\ub2e4. \uc608\ub97c \ub4e4\uc5b4 \ub370\uc774\ud130 \ud504\ub808\uc784\uc774\ub77c\ub294 \ub370\uc774\ud130 \uad6c\uc870\uc758 \uc77c\ubd80\ubd84\uc744 \ucc38\uc870\ud558\uae30 \uc704\ud55c \ubc29\ubc95\uc740 <code>df[1]<\/code>, <code>df[&quot;colname&quot;]<\/code>, <code>df[[&quot;colname&quot;]]<\/code>, <code>df[[1]]<\/code>, <code>df[1,2]<\/code>, <code>df[&quot;rowname&quot;, &quot;colname&quot;]<\/code>, <code>df$colname<\/code>, <code>df[df$colname&gt;1,]<\/code> \ub4f1 \uad49\uc7a5\ud788 \ub2e4\uc591\ud569\ub2c8\ub2e4. \uadf8\ub9ac\uace0 \ub3d9\uc77c\ud55c \ubc29\ubc95\uc774 \ub2e4\ub978 \ub370\uc774\ud130 \uad6c\uc870(\ud589\ub82c, \ub9ac\uc2a4\ud2b8 \ub4f1)\uc5d0\ub3c4 \uc0ac\uc6a9\ub420 \uc218 \uc788\ub294 \uacbd\uc6b0\uac00 \uc788\ub294 \ubc18\uba74, \uc0ac\uc6a9\ud560 \uc218 \uc5c6\uae30\ub3c4 \ud569\ub2c8\ub2e4. \ud558\uc9c0\ub9cc \uc774\ub97c \uad6c\ubd84\ud558\ub294 \uc6d0\ub9ac\uac00 \ubb34\uc5c7\uc77c\uae4c\uc694? \uc81c\uac00 R\uc744 \ubc30\uc6b8 \ub54c\ub3c4 \uadf8\ub807\uace0, \ub2f9\uc2dc\uc758 \ub300\ubd80\ubd84\uc758 \ucc45\uc740 \u201c\uc774\ub7f0 \uac78 \ud558\ub824\uba74 \uc774\ub807\uac8c \ud574\u201d \ub610\ub294 \u201c\uc774\ub7f0 \uae30\ub2a5\ub4e4\uc774 \uc788\uc5b4\u201d\uac00 \ub2e4\uc600\uc2b5\ub2c8\ub2e4. \uacbd\uc6b0\uc5d0 \ub530\ub77c \uc870\uae08\uc529 \ub2ec\ub77c\uc9c0\ub294 \ubb38\ubc95\uc744 \uc774\ud574\ud558\uc9c0 \ubabb\ud558\uba74 \uadf8\ub0e5 \uc678\uc6cc\uc57c \ud558\ub294\ub370, \uc544\ubb34 \uc0dd\uac01\uc5c6\uc774 \uc678\uc6b0\uae30\uc5d0\ub294 \ub108\ubb34 \ubd84\ub7c9\uc774 \ub9ce\uc558\uc8e0. \uadf8\ub9ac\uace0 \ud575\uc2ec\uc801\uc778 \uc6d0\ub9ac\ub97c \uc774\ud574\ud558\uc9c0 \ubabb\ud558\uace0 \uadf8\ub54c \uadf8\ub54c \uc784\uc2dc\ubcc0\ud1b5\uc73c\ub85c \ud504\ub85c\uadf8\ub7a8\uc744 \uc9dc\uac8c \ub418\uba74 \ucc3e\uae30\ub3c4 \ud798\ub4e0 \ub17c\ub9ac\uc801 \uc624\ub958(\ub610\ub294 \ubc84\uadf8)\uac00 \uc0dd\uae30\uac8c \ub9c8\ub828\uc774\uace0, \uc774\ub7f0 \ubc84\uadf8\uac00 \uc0dd\uae30\uba74 \ubd80\ud638 \ud558\ub098, \ud568\uc218 \ud558\ub098 \ub54c\ubb38\uc5d0 \uba38\ub9ac\ub97c \uc950\uc5b4\uc9dc\uba70 \uace0\uc0dd\uc744 \ud558\uac8c \ub429\ub2c8\ub2e4.<\/p>\n<h2>\uc8fc\uc694 \ub0b4\uc6a9 \uc18c\uac1c<\/h2>\n<ul>\n<li>\n<p>\ub0a0\uc9dc\uc640 \uc2dc\uac04<\/p>\n<\/li>\n<li>\n<p><code>data.table<\/code> \ud328\ud0a4\uc9c0<\/p>\n<\/li>\n<li>\n<p>\ubb38\uc790\uc5f4 <\/p>\n<\/li>\n<li>\n<p>\uc815\uaddc\ud45c\ud604\uc2dd<\/p>\n<\/li>\n<li>\n<p><code>ggplot2<\/code><\/p>\n<\/li>\n<\/ul>\n<h2>\uc624\ub298\uc758 \uc8fc\uc81c?!<\/h2>\n<ul>\n<li>\n<p><a href=\"https:\/\/youtu.be\/ho7oagHeqNc?t=1216\">Category Theory in Life &#8211; Eugenia Cheng<\/a><\/p>\n<\/li>\n<li>\n<p>\uc218\ud559\uc5d0\uc11c \uac00\uc7a5 \uba85\ubc31\ud55c \uc0ac\uc2e4, \\(x=x\\)!<\/p>\n<ul>\n<li>\uc218\ud559\uacc4\uc758 &ldquo;<strong>\ub098\ub294 \uc0dd\uac01\ud55c\ub2e4. \uace0\ub85c \ub098\ub294 \uc874\uc7ac\ud55c\ub2e4!<\/strong>&rdquo;<\/li>\n<li>\uc758\uc2ec\ud560 \ub098\uc704 \uc5c6\uc774 \uba85\ubc31\ud55c \uc0ac\uc2e4???<\/li>\n<\/ul>\n<\/li>\n<li>\n<p>R\uc5d0\uc11c\ub3c4 <code>x&lt;-y; x==y<\/code>\ub294 \ud56d\uc0c1 \ucc38(<code>TRUE<\/code>)\uc77c\uae4c?<\/p>\n<\/li>\n<\/ul>\n<h2><code>x&lt;-y; x==y<\/code><\/h2>\n<pre><code class=\"r\">test = function(x) {\n  y &lt;- x\n  return(x==y)\n}\ntest(3)\ntest(NA)\ntest(NaN)\ntest(NULL)\n<\/code><\/pre>\n<pre>## [1] TRUE\n## [1] NA\n## [1] NA\n## logical(0)\n<\/pre>\n<p><code>NA<\/code>\ub294 \uacb0\uce21\uce58\ub97c \uc758\ubbf8\ud558\uace0, \ub9c8\uce58 \uc218\ud559\uc758 \ubbf8\uc9c0\uc218 \\(x\\) \uc640 \uac19\ub2e4. <code>NA==NA<\/code>\uac00 <code>NA<\/code>\uac00 \ub418\ub294 \uc0c1\ud669\uc740 \ub9c8\uce58 \uc218\ud559\uc5d0\uc11c \uba85\uc81c \\(x=y\\) \uc758 \uc9c4\uc704\ub97c \ud310\uc815\ud558\ub294 \uac83\uacfc \ube44\uc2b7\ud55c \ub4ef \ud569\ub2c8\ub2e4. \ubc18\uba74 \\(x \\in A\\) \ub97c \uc758\ubbf8\ud558\ub294 <code>%in%<\/code> \uc5f0\uc0b0\uc5d0\uc11c\ub294 \ub2e4\ub974\uac8c \uc791\ub3d9\ud569\ub2c8\ub2e4! $x \\in { x } $ \ub97c \uc0dd\uac01\ud560 \ub54c, <code>NA %in% NA<\/code>\ub294 <code>NA<\/code>\ub97c \uc218\ud559\uc5d0\uc11c \ubbf8\uc9c0\uc218 \\(x\\) \ub85c \uc0dd\uac01\ud560 \ub54c, \\(x \\in {x}\\) \uc640 \ube44\uc2b7\ud558\uac8c \uc791\ub3d9\ud558\ub294 \uac83\uc774\uc8e0.<\/p>\n<pre><code class=\"r\">test = function(x) {\n  y &lt;- x\n  return(x %in% y)\n}\ntest(3)\ntest(NA)\ntest(NaN)\ntest(NULL)\n<\/code><\/pre>\n<pre>## [1] TRUE\n## [1] TRUE\n## [1] TRUE\n## logical(0)\n<\/pre>\n<p>\ub2e4\uc74c\uc758 \uacb0\uacfc\ub97c \ubcf4\uace0 R\uc774 \uc65c \uadf8\ub807\uac8c \uc791\ub3d9\ud558\ub294\uc9c0 \uc0dd\uac01\ud574\ubd05\uc2dc\ub2e4.<\/p>\n<pre><code class=\"r\">x= NA\nx | TRUE\nx &amp; FALSE\nx | !x\n<\/code><\/pre>\n<pre>## [1] TRUE\n## [1] FALSE\n## [1] NA\n<\/pre>\n<p>\ub2e4\uc74c\uc740 \uc218\ud559\uc801\uc73c\ub85c \uc633\uc740 \uacb0\uacfc\uc77c\uae4c\uc694?<\/p>\n<pre><code class=\"r\">1\/0\n<\/code><\/pre>\n<pre>## [1] Inf\n<\/pre>\n<h2>\uc815\uaddc\ud45c\ud604\uc2dd\uc758 \uae30\ucd08<\/h2>\n<p>\uc815\uaddc\ud45c\ud604\uc2dd\uc744 \ubb38\uc790\uc5f4\uc744 \ud65c\uc6a9\ud574 \ubb38\uc790\uc5f4\uc758 \ud328\ud134\uc744 \ub098\ud0c0\ub0b4\uae30 \ub54c\ubb38\uc5d0 \ubb38\uc790 \uc911\uc758 \uc77c\ubd80\ub97c <strong>\ud328\ud134<\/strong>\uc744 \ub098\ud0c0\ub0b4\uae30 \uc704\ud574 \uc0ac\uc6a9\ud55c\ub2e4. \ub2e4\uc74c\uc758 \ubb38\uc790\ub4e4\uc740 \uc815\uaddc\ud45c\ud604\uc2dd\uc5d0\uc11c <strong>\ubb38\uc790 \uadf8\ub300\ub85c\uc758 \ubb38\uc790<\/strong>\ub97c \uc758\ubbf8\ud558\uc9c0 \uc54a\ub294\ub2e4.<\/p>\n<pre>. [ ] \\ { } * + ? ^ $ ( ) |\n<\/pre>\n<p>\uc5ec\uae30\uc11c\ub294 \uc774\ub4e4 \ubb38\uc790\ub97c <strong>\ubb38\uc790 \uadf8\ub300\ub85c\uc758 \ubb38\uc790<\/strong>\ub85c \uc0ac\uc6a9\ud558\ub824\uba74 \uc5b4\ub5bb\uac8c \ud574\uc57c \ud558\ub294\uc9c0 \uc54c\uc544\ubd05\uc2dc\ub2e4. <\/p>\n<ol>\n<li>\uac00\uc7a5 \uc26c\uc6b4 \ubc29\ubc95\uc740 <code>fixed=TRUE<\/code>\ub85c \ub193\ub294 \uac83\uc785\ub2c8\ub2e4. <\/li>\n<\/ol>\n<pre><code class=\"r\">grepl(pattern=&#39;.&#39;, c(&#39;abc&#39;, &#39;ab.c&#39;))\n<\/code><\/pre>\n<pre>## [1] TRUE TRUE\n<\/pre>\n<ol>\n<li>\ud558\uc9c0\ub9cc \uc815\uaddc\ud45c\ud604\uc2dd\uc5d0\uc11c\ub294 \ud56d\uc0c1 <code>grepl(x, x)<\/code>\uac00 <code>TRUE<\/code>\uac00 \ub418\uc9c0 \uc54a\uc2b5\ub2c8\ub2e4. \uc65c\ub0d0\ud558\uba74 \uc704\uc5d0\uc11c \ubd24\ub358 \uae30\ud638\ub4e4 \ub54c\ubb38\uc774\uc9c0\uc694. <\/li>\n<\/ol>\n<p>\uc0ac\uc2e4 \uc774 \ubd80\ubd84\uc740 \uc815\uaddc\ud45c\ud604\uc2dd\uc744 \uc2e4\uc81c\ub85c \uc0ac\uc6a9\ud560 \ub54c \uac00\ub054 \ubd80\ub52a\ud788\uac8c \ub418\ub294 \ubb38\uc81c\uc774\uace0, \uc801\uc808\ud55c \uacbd\ud5d8 \uc5c6\uc774 \uc815\uaddc\ud45c\ud604\uc2dd\uc744 \uc0ac\uc6a9\ud558\uba74 \uc624\ub958\uac00 \ubc1c\uc0dd\ub418\uae30 \uc27d\uace0, \uadf8 \uc624\ub958\ub97c \ucc3e\uc544\ub0b4\uae30 \uc704\ud574 \ub9ce\uc740 \uc2dc\uac04\uc744 \ud5c8\ube44\ud574\uc57c \ud568\uc5d0\ub3c4 \ubd88\uad6c\ud558\uace0 \uc815\uaddc\ud45c\ud604\uc2dd\uc744 \uc124\uba85\ud558\ub294 \ub9ce\uc740 \ubb38\uc11c\uc5d0\uc11c \ub204\ub77d\ud558\uace0 \uc788\ub294 \ubd80\ubd84\uc774\uae30\ub3c4 \ud569\ub2c8\ub2e4.<\/p>\n<p>\uc77c\ub2e8 \uc2e4\ud5d8\uc744 \ud574\ubd05\uc2dc\ub2e4.<\/p>\n<pre><code class=\"r\">library(dplyr)\nlibrary(stringr)\n\nsymbols &lt;- &quot;.[]\\\\{}*+?^$()|&quot;\n\nfor (i in 1:nchar(symbols)) {\n  x &lt;- substr(symbols, i, i)\n  y &lt;- x\n  tryCatch({\n    z &lt;- grepl(x, x)\n    if (!z) {\n      cat(paste0(&quot;grepl(&quot;, x, &quot;,&quot;, x, &quot;) is FALSE!\\n&quot;))\n    }\n\n  }, warning = function(warning_condition) {\n    cat(paste0(&quot;grepl(&quot;, x, &quot;,&quot;, x, &quot;) produce WARNING!\\n&quot;))\n    #print(warning_condition); print(z1); print(z2)\n    #cat(i, &quot;\\n&quot;)\n  }, error = function(error_condition) {\n    cat(paste0(&quot;grepl(&quot;, x, &quot;,&quot;, x, &quot;) produce ERROR!\\n&quot;))\n    #print(error_condition); print(z1); print(z2)\n    #cat(i, &quot;\\n&quot;)\n  })}\n<\/code><\/pre>\n<pre>## grepl([,[) produce ERROR!\n## grepl(\\,\\) produce ERROR!\n## grepl({,{) produce ERROR!\n## grepl((,() produce ERROR!\n<\/pre>\n<p>\uc5b4\ub78f! \uc774 \uacb0\uacfc\ub9cc \ubcf4\uba74 \ub2e8\uc9c0 4\uac1c\uc758 \ubb38\uc790\ub97c \uc81c\uc678\ud558\uace0\ub294 <code>grepl(x,x)<\/code>\uc774 <code>TRUE<\/code>\uc785\ub2c8\ub2e4! \ud558\uc9c0\ub9cc <code>TRUE<\/code>\ub77c\uace0 \ubb38\uc81c\uac00 \uc5c6\ub294 \uac83\uc740 \uc544\ub2c8\ub2e4. <strong>\uac19\uc740 \uac83\uc744 \uac19\ub2e4\uace0 \ud558\ub294 \uac83\uc73c\ub85c\ub294 \ubd80\uc871\ud558\ub2e4.<\/strong> (\uc774\uac74 \uc77c\uc885\uc758 \ud655\uc99d\ud3b8\ud5a5\uc77c \uc218 \uc788\ub2e4.) <strong>\ub2e4\ub978 \uac83\ub3c4 \ub2e4\ub974\ub2e4\uace0 \ud574\uc57c \ud55c\ub2e4!<\/strong><\/p>\n<pre><code class=\"r\">library(dplyr)\nlibrary(stringr)\n\nsymbols &lt;- &quot;.[]\\\\{}*+?^$()|&quot;\n\nfor (i in 1:nchar(symbols)) {\n  x &lt;- substr(symbols, i, i)\n  y &lt;- &quot;a&quot;\n  tryCatch({\n    z &lt;- grepl(x, y)\n    if (z) {\n      cat(paste0(&quot;grepl(&quot;, x, &quot;,&quot;, y, &quot;) is TRUE!\\n&quot;))\n    }\n\n  }, warning = function(warning_condition) {\n    cat(paste0(&quot;grepl(&quot;, x, &quot;,&quot;, y, &quot;) produce WARNING!\\n&quot;))\n    #print(warning_condition); print(z1); print(z2)\n    #cat(i, &quot;\\n&quot;)\n  }, error = function(error_condition) {\n    cat(paste0(&quot;grepl(&quot;, x, &quot;,&quot;, y, &quot;) produce ERROR!\\n&quot;))\n    #print(error_condition); print(z1); print(z2)\n    #cat(i, &quot;\\n&quot;)\n  })}\n<\/code><\/pre>\n<pre>## grepl(.,a) is TRUE!\n## grepl([,a) produce ERROR!\n## grepl(\\,a) produce ERROR!\n## grepl({,a) produce ERROR!\n## grepl(*,a) is TRUE!\n## grepl(+,a) is TRUE!\n## grepl(?,a) is TRUE!\n## grepl(^,a) is TRUE!\n## grepl($,a) is TRUE!\n## grepl((,a) produce ERROR!\n## grepl(|,a) is TRUE!\n<\/pre>\n<p>\ubb50 \uc774\ub7f0 \uac83 \uae4c\uc9c0 \uc54c \ud544\uc694\uac00 \uc788\uc744\uae4c \uc2f6\uc744 \uc218\ub3c4 \uc788\uc744 \uac83\uc785\ub2c8\ub2e4. \ud558\uc9c0\ub9cc \uc81c \uacbd\ud5d8 \uc0c1 \uc624\ub958\ub97c \ubc29\uc9c0\ud558\ub294\ub370 \ub3c4\uc6c0\uc774 \ub429\ub2c8\ub2e4.<\/p>\n<p>\uc608\ub97c \ub4e4\uc5b4 \uc22b\uc790\uc5d0 <code>|<\/code>\ub85c \ub05d\ub098\ub294 \ud328\ud134\uc744 \ucc3e\uc744 \ub54c, <code>|<\/code> \uc55e\uc5d0 <code>\\<\/code>\ub97c \ube7c\ub193\uc744 \uc218 \uc788\uc2b5\ub2c8\ub2e4. \uadf8\ub807\uac8c \ud558\uba74 \uc5b4\ub5bb\uac8c \ub420\uae4c\uc694? \uc5b4\uca0b\ub4e0 \uc22b\uc790\uac00 \ub4e4\uc5b4\uac04 \ud328\ud134\uc744 \ucc3e\uc744 \uac83\uc774\ub77c\uace0 \uc548\uc774\ud558\uac8c \uc0dd\uac01\ud558\uba74 \uc548 \ub429\ub2c8\ub2e4.<\/p>\n<pre><code class=\"r\">grepl(&#39;\\\\d+|&#39;, c(&#39;2341|&#39;, &#39;23411&#39;))\n<\/code><\/pre>\n<pre>## [1] TRUE TRUE\n<\/pre>\n<p>\uc774\uac83\ub9cc \ubcf4\uba74, &ldquo;\uac70\ubd10, \uc22b\uc790\uac00 \ub4e4\uc5b4\uac04 \uac78 \ucc3e\uc796\uc544?&quot;\ub77c\uace0 \ub9d0\ud560\uc9c0 \ubaa8\ub985\ub2c8\ub2e4. \ud558\uc9c0\ub9cc \ub2e4\uc74c\uc744 \ubd05\uc2dc\ub2e4.<\/p>\n<pre><code class=\"r\">grepl(&#39;\\\\d+|&#39;, c(&#39;abc&#39;, &#39;.+...&#39;))\n<\/code><\/pre>\n<pre>## [1] TRUE TRUE\n<\/pre>\n<p>\ub610\ub294 \uae34 \uc815\uaddc\ud45c\ud604\uc2dd\uc5d0\uc11c <code>)<\/code>\ub97c \ud558\ub098\ucbe4 \ub354 \uc9d1\uc5b4\ub123\ub294\ub2e4\uba74 \uc5b4\ub5bb\uac8c \ub420\uae4c\uc694? \uc55e\uc758 <code>(<\/code>\uc640 \uc30d\uc774 \ub9de\uc9c0 \uc54a\ub294 <code>)<\/code>\ub294 \uc5d0\ub7ec\uac00 \ub0a0 \uac70\ub77c\uace0 \uc548\uc774\ud558\uac8c \uc0dd\uac01\ud558\uba74 \uc548 \ub429\ub2c8\ub2e4.<\/p>\n<pre><code class=\"r\">grepl(&#39;(\\\\d+))&#39;, c(&#39;1234&#39;, &#39;1234)&#39;))\n<\/code><\/pre>\n<pre>## [1] FALSE  TRUE\n<\/pre>\n<p>\uc774 \uacb0\uacfc\ub97c \ubcf4\uace0 \ub098\ub2c8 \uacfc\uc5f0 \uc704\uc5d0\uc11c \uc5f4\uac70\ud55c \ubaa8\ub4e0 \uae30\ud638\uc5d0 \ub300\ud574 <code>\\<\/code>\ub97c \uc55e\uc5d0 \ubd99\uc774\uba74 \ubb38\uc790 \uadf8\ub300\ub85c \uae30\ud638\uac00 \ub418\ub294\uc9c0\uc5d0 \ub300\ud574 \uc758\uad6c\uc2ec\uc774 \uc0dd\uacbc\ub2e4. \ubb50 \ud574\ubcf4\ub294 \uc218 \ubc16\uc5d0.<\/p>\n<pre><code class=\"r\">library(dplyr)\nlibrary(stringr)\n\nsymbols &lt;- &quot;.[]\\\\{}*+?^$()|&quot;\n\nfor (i in 1:nchar(symbols)) {\n  x &lt;- substr(symbols, i, i)\n  y &lt;- paste0(&#39;\\\\&#39;, x)\n  tryCatch({\n    z1 &lt;- grepl(y, x)\n    z2 &lt;- grepl(y, &#39;a&#39;)\n    if (!z1) {\n      cat(paste0(&quot;grepl(&quot;, y, &quot;,&quot;, x, &quot;) is FALSE!\\n&quot;))\n    }\n    if (z2) {\n      cat(paste0(&quot;grepl(&quot;, y, &quot;, a) is TRUE!\\n&quot;))\n    }\n\n  }, warning = function(warning_condition) {\n    cat(paste0(&quot;grepl(&quot;, y, &quot;,&quot;, x, &quot;) produce WARNING!\\n&quot;))\n    #print(warning_condition); print(z1); print(z2)\n    #cat(i, &quot;\\n&quot;)\n  }, error = function(error_condition) {\n    cat(paste0(&quot;grepl(&quot;, y, &quot;,&quot;, x, &quot;) produce ERROR!\\n&quot;))\n    #print(error_condition); print(z1); print(z2)\n    #cat(i, &quot;\\n&quot;)\n  })}\n<\/code><\/pre>\n<p>\uc544\ubb34\uac83\ub3c4 \ub098\uc624\uc9c0 \uc54a\ub294 \uac83\ubcf4\ub2c8 \uc704\uc5d0\uc11c \uc5f4\uac70\ud55c \ubaa8\ub4e0 \uae30\ud638\uc5d0 \ub300\ud574 <code>\\<\/code>\ub97c \uc55e\uc5d0 \ubd99\uc774\uba74 \ubb38\uc790 \uadf8\ub300\ub85c\uc758 \uc758\ubbf8\ub97c \ub73b\ud569\ub2c8\ub2e4.<\/p>\n<p>\uadf8\ub807\ub2e4\uba74 <code>[<\/code>, <code>]<\/code> \uc548\uc5d0\uc11c\ub294 \uc5b4\ub5a8\uae4c\uc694? <\/p>\n<p>ERE\ub294 <code>[<\/code>, <code>]<\/code> \uc548\uc5d0\uc11c \ubaa8\ub4e0 \ubb38\uc790\uac00 \ubb38\uc790 \uadf8\ub300\ub85c\uc758 \ubb38\uc790\ub97c \uc758\ubbf8\ud569\ub2c8\ub2e4. \uc774\uac83\uc740 PCRE(Perl-Compatible Regular Expression)\uacfc\uc758 \ud070 \ucc28\uc774\uc810\uc774\uae30\ub3c4 \ud558\uc8e0. \uadf8\ub798\uc11c PCRE\ub97c \uc4f0\uba74 <code>[<\/code>,<code>]<\/code>\uc548\uc5d0\uc11c\ub3c4 <code>\\<\/code>\ub97c \ub098\ud0c0\ub0b4\uae30 \uc704\ud574 <code>\\\\\\\\<\/code>\ub97c \uc368\uc57c \ud569\ub2c8\ub2e4!!!<\/p>\n<pre><code class=\"r\">grepl(&quot;[\\\\a]&quot;, c(&quot;\\\\&quot;, &quot;a&quot;, &quot;b&quot;))\n<\/code><\/pre>\n<pre>## [1]  TRUE  TRUE FALSE\n<\/pre>\n<pre><code class=\"r\">grepl(&quot;[\\\\a]&quot;, c(&quot;\\\\&quot;, &quot;a&quot;, &quot;b&quot;), perl=TRUE)\n<\/code><\/pre>\n<pre>## [1] FALSE FALSE FALSE\n<\/pre>\n<pre><code class=\"r\">grepl(&quot;[\\\\\\\\a]&quot;, c(&quot;\\\\&quot;, &quot;a&quot;, &quot;b&quot;), perl=TRUE)\n<\/code><\/pre>\n<pre>## [1]  TRUE  TRUE FALSE\n<\/pre>\n<p>\uadf8\ub807\ub2e4\uba74 \\(x \\neq y\\) \uc774\uba74 <code>x!=y<\/code>\uac00 \ud56d\uc0c1 \uc131\ub9bd\ud560\uae4c\uc694? \ud639\uc740 \\(x \\neq y\\) \uc774\uba74 \ud56d\uc0c1 <code>x!=y<\/code>\uac00 \ub418\ub294 \uac83\uc774 \uc88b\uc740 \uac83\uc77c\uae4c\uc694?<\/p>\n<p>\ub2e4\uc74c\uc758 \ud14d\uc2a4\ud2b8\ub97c \ubd05\uc2dc\ub2e4. \ud569\uc790(ligature; \ub9ac\uac70\uccd0)[<sup>2]\ub098<\/sup> \uc6c0\ub77c\uc6b0\ud2b8\uac00 \ub530\ub85c \ud639\uc740 \ud569\uccd0 \uc788\ub294 \ubb38\uc790\uc758 \uacbd\uc6b0(pdf\uc5d0\uc11c \ubcf5\uc0ac \ubd99\uc5ec\ub123\uae30\ud558\uba74 \ubcfc \uc218 \uc788\uc8e0)\uc5d0\ub294 \ub2e4\ub978 \uac78 \ub2e4\ub974\ub2e4\uace0 \ud558\ub294 \uac8c \uaf2d \uc88b\uc740 \uac8c \uc544\ub2c8\uc8e0.<\/p>\n<pre><code class=\"r\">x &lt;- c(&quot;He sni\\ufb00ed.&quot;, &quot;\\u00fc&quot;)\ny &lt;- c(&quot;He sniffed.&quot;, &quot;u\\u0308&quot;)\nx == y\n<\/code><\/pre>\n<pre>## [1] FALSE FALSE\n<\/pre>\n<p><img src=\"data:image\/png;base64,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\" alt=\"\"\/><\/p>\n<p>\uc774\ub7f4 \ub550 \uc5b4\ub5bb\uac8c \ud574\uc57c \ud560\uae4c\uc694?<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\uc0c8\ucc45 \uc18c\uac1c (R\ub85c \ud558\ub294 \ube45\ub370\uc774\ud130 \ubd84\uc11d)[1] \uc81c\ubaa9 : R\ub85c \ud558\ub294 \ube45\ub370\uc774\ud130 \ubd84\uc11d: \ub370\uc774\ud130 \uc804\ucc98\ub9ac\uc640 \uc2dc\uac01\ud654 \ucd9c\ud310\uc0ac : \uc228\uc740\uc6d0\ub9ac \uc9c0\uc74c : \uae40\uad8c\ud604 \ucabd\uc218 : 328\ucabd \ubc1c\ud589\uc77c : 2019\ub144 3\uc6d4 1\uc77c ISBN : 979-11-960144-7-6(93000) \uc774 \ud3ec\uc2a4\ud2b8\uc758 \uc8fc\uc18c : http:\/\/141.164.34.82\/?p=905 [1]: \uc774 \ud3ec\uc2a4\ud2b8(post)\ub294 2019\ub144 2\uc6d4 20\uc77c \ubc1c\ud45c \ub0b4\uc6a9\uc785\ub2c8\ub2e4. \uc9c0\uc740\uc774 \uc18c\uac1c \uc774\ub984 : \uae40\uad8c\ud604 \uc11c\uc6b8\ub300 \uc778\uc9c0\uacfc\ud559 \ubc15\uc0ac \uc11c\uac15\ub300, \uad6d\ubbfc\ub300, [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":944,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[28,79],"tags":[158,156,155,157],"jetpack_featured_media_url":"http:\/\/ds.sumeun.org\/wp-content\/uploads\/2019\/02\/equalities.png","_links":{"self":[{"href":"http:\/\/ds.sumeun.org\/index.php?rest_route=\/wp\/v2\/posts\/905"}],"collection":[{"href":"http:\/\/ds.sumeun.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/ds.sumeun.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/ds.sumeun.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/ds.sumeun.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=905"}],"version-history":[{"count":4,"href":"http:\/\/ds.sumeun.org\/index.php?rest_route=\/wp\/v2\/posts\/905\/revisions"}],"predecessor-version":[{"id":1920,"href":"http:\/\/ds.sumeun.org\/index.php?rest_route=\/wp\/v2\/posts\/905\/revisions\/1920"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/ds.sumeun.org\/index.php?rest_route=\/wp\/v2\/media\/944"}],"wp:attachment":[{"href":"http:\/\/ds.sumeun.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=905"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/ds.sumeun.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=905"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/ds.sumeun.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=905"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}