{"id":1314,"date":"2023-07-26T22:01:06","date_gmt":"2023-07-26T22:01:06","guid":{"rendered":"https:\/\/statorials.org\/pt\/python-remoto-de-cozinha\/"},"modified":"2023-07-26T22:01:06","modified_gmt":"2023-07-26T22:01:06","slug":"python-remoto-de-cozinha","status":"publish","type":"post","link":"https:\/\/statorials.org\/pt\/python-remoto-de-cozinha\/","title":{"rendered":"Como calcular a dist\u00e2ncia de cook em python"},"content":{"rendered":"<p><\/p>\n<hr>\n<p><span style=\"color: #000000;\"><strong>A dist\u00e2ncia de Cook<\/strong> \u00e9 usada para identificar <a href=\"https:\/\/statorials.org\/pt\/observacao-em-estatisticas\/\" target=\"_blank\" rel=\"noopener\">observa\u00e7\u00f5es<\/a> influentes em um modelo de regress\u00e3o.<\/span><\/p>\n<p> <span style=\"color: #000000;\">A f\u00f3rmula para a dist\u00e2ncia de Cook \u00e9:<\/span><\/p>\n<p style=\"text-align: center;\"> <span style=\"color: #000000;\"><strong>d <sub>i<\/sub><\/strong> = (r <sub>i<\/sub> <sup>2<\/sup> \/ p*MSE) * (h <sub>ii<\/sub> \/ (1-h <sub>ii<\/sub> ) <sup>2<\/sup> )<\/span><\/p>\n<p> <span style=\"color: #000000;\">Ouro:<\/span><\/p>\n<ul>\n<li> <span style=\"color: #000000;\"><strong>ri<\/strong> \u00e9 <sub><strong>o<\/strong><\/sub> i- <sup>\u00e9simo<\/sup> res\u00edduo<\/span><\/li>\n<li> <span style=\"color: #000000;\"><strong>p<\/strong> \u00e9 o n\u00famero de coeficientes no modelo de regress\u00e3o<\/span><\/li>\n<li> <span style=\"color: #000000;\"><strong>MSE<\/strong> \u00e9 o erro quadr\u00e1tico m\u00e9dio<\/span><\/li>\n<li> <span style=\"color: #000000;\"><strong>h<\/strong> <sub>ii<\/sub> \u00e9 o <sup>i-<\/sup> \u00e9simo valor de alavancagem<\/span><\/li>\n<\/ul>\n<p> <span style=\"color: #000000;\">Essencialmente, a dist\u00e2ncia de Cook mede o quanto todos os valores ajustados do modelo mudam quando a i- <sup>\u00e9sima<\/sup> observa\u00e7\u00e3o \u00e9 removida.<\/span><\/p>\n<p> <span style=\"color: #000000;\">Quanto maior o valor da dist\u00e2ncia de Cook, mais influente \u00e9 uma determinada observa\u00e7\u00e3o.<\/span><\/p>\n<p> <span style=\"color: #000000;\">Como regra geral, qualquer observa\u00e7\u00e3o com dist\u00e2ncia de Cook superior a 4\/n (onde <em>n<\/em> = total de observa\u00e7\u00f5es) \u00e9 considerada como tendo uma grande influ\u00eancia.<\/span><\/p>\n<p> <span style=\"color: #000000;\">Este tutorial fornece um exemplo passo a passo de como calcular a dist\u00e2ncia de Cook para um determinado modelo de regress\u00e3o em Python.<\/span><\/p>\n<h3> <span style=\"color: #000000;\"><strong>Passo 1: Insira os dados<\/strong><\/span><\/h3>\n<p> <span style=\"color: #000000;\">Primeiro, criaremos um pequeno conjunto de dados para trabalhar em Python:<\/span><\/p>\n<pre style=\"background-color: #ececec; font-size: 15px;\"> <strong><span style=\"color: #008000;\">import<\/span> pandas <span style=\"color: #008000;\">as<\/span> pd\n\n<span style=\"color: #008080;\">#create dataset\n<\/span>df = pd. <span style=\"color: #3366ff;\">DataFrame<\/span> ({' <span style=\"color: #008000;\">x<\/span> ': [8, 12, 12, 13, 14, 16, 17, 22, 24, 26, 29, 30],\n                   ' <span style=\"color: #008000;\">y<\/span> ': [41, 42, 39, 37, 35, 39, 45, 46, 39, 49, 55, 57]})\n<\/strong><\/pre>\n<h3> <span style=\"color: #000000;\"><strong>Passo 2: Ajustar o modelo de regress\u00e3o<\/strong><\/span><\/h3>\n<p> <span style=\"color: #000000;\">A seguir, ajustaremos um <a href=\"https:\/\/statorials.org\/pt\/regressao-linear-simples-em-python\/\" target=\"_blank\" rel=\"noopener\">modelo de regress\u00e3o linear simples<\/a> :<\/span><\/p>\n<pre style=\"background-color: #ececec; font-size: 15px;\"> <span style=\"color: #000000;\"><strong><span style=\"color: #008000;\">import<\/span> statsmodels. <span style=\"color: #3366ff;\">api<\/span> <span style=\"color: #008000;\">as<\/span> sm\n\n<span style=\"color: #008080;\">#define response variable\n<\/span>y = df[' <span style=\"color: #008000;\">y<\/span> ']\n\n<span style=\"color: #008080;\">#define explanatory variable\n<\/span>x = df[' <span style=\"color: #008000;\">x<\/span> ']\n\n<span style=\"color: #008080;\">#add constant to predictor variables\n<\/span>x = sm. <span style=\"color: #3366ff;\">add_constant<\/span> (x)\n\n<span style=\"color: #008080;\">#fit linear regression model\n<\/span>model = sm. <span style=\"color: #3366ff;\">OLS<\/span> (y,x). <span style=\"color: #3366ff;\">fit<\/span> ()<\/strong><\/span><\/pre>\n<h3> <span style=\"color: #000000;\"><strong>Etapa 3: calcular a dist\u00e2ncia de cozimento<\/strong><\/span><\/h3>\n<p> <span style=\"color: #000000;\">A seguir, calcularemos a dist\u00e2ncia de Cook para cada observa\u00e7\u00e3o do modelo:<\/span><\/p>\n<pre style=\"background-color: #ececec; font-size: 15px;\"> <strong><span style=\"color: #008080;\">#suppress scientific notation\n<span style=\"color: #000000;\"><span style=\"color: #008000;\">import<\/span> numpy <span style=\"color: #008000;\">as<\/span> np\nn.p. <span style=\"color: #3366ff;\">set_printoptions<\/span> (suppress= <span style=\"color: #008000;\">True<\/span> )\n\n<span style=\"color: #008080;\">#create instance of influence\n<\/span>influence = model. <span style=\"color: #3366ff;\">get_influence<\/span> ()\n\n<span style=\"color: #008080;\">#obtain Cook's distance for each observation\n<\/span>cooks = influence. <span style=\"color: #3366ff;\">cooks_distance<\/span>\n\n<span style=\"color: #008080;\">#display Cook's distances\n<\/span><span style=\"color: #993300;\">print<\/span> (cooks)\n\n(array([0.368, 0.061, 0.001, 0.028, 0.105, 0.022, 0.017, 0. , 0.343,\n        0. , 0.15 , 0.349]),\n array([0.701, 0.941, 0.999, 0.973, 0.901, 0.979, 0.983, 1. , 0.718,\n        1. , 0.863, 0.713]))\n<\/span><\/span><\/strong><\/pre>\n<p> <span style=\"color: #000000;\">Por padr\u00e3o, a fun\u00e7\u00e3o <strong>cooks_distance()<\/strong> exibe uma matriz de valores para a dist\u00e2ncia de Cook para cada observa\u00e7\u00e3o seguida por uma matriz de valores p correspondentes.<\/span><\/p>\n<p> <span style=\"color: #000000;\">Por exemplo:<\/span><\/p>\n<ul>\n<li> <span style=\"color: #000000;\">Dist\u00e2ncia de Cook para observa\u00e7\u00e3o n\u00ba 1: <strong>0,368<\/strong> (valor p: 0,701)<\/span><\/li>\n<li> <span style=\"color: #000000;\">Dist\u00e2ncia de Cook para observa\u00e7\u00e3o n\u00ba 2: <strong>0,061<\/strong> (valor p: 0,941)<\/span><\/li>\n<li> <span style=\"color: #000000;\">Dist\u00e2ncia de Cook para observa\u00e7\u00e3o n\u00ba 3: <strong>0,001<\/strong> (valor p: 0,999)<\/span><\/li>\n<\/ul>\n<p> <span style=\"color: #000000;\">E assim por diante.<\/span><\/p>\n<h3> <span style=\"color: #000000;\"><strong>Passo 4: Visualize as dist\u00e2ncias do cozinheiro<\/strong><\/span><\/h3>\n<p> <span style=\"color: #000000;\">Por fim, podemos criar um gr\u00e1fico de dispers\u00e3o para visualizar os valores da vari\u00e1vel preditora em fun\u00e7\u00e3o da dist\u00e2ncia de Cook para cada observa\u00e7\u00e3o:<\/span> <\/p>\n<pre style=\"background-color: #ececec; font-size: 15px;\"> <strong><span style=\"color: #008080;\"><span style=\"color: #000000;\"><span style=\"color: #008000;\">import<\/span> matplotlib. <span style=\"color: #3366ff;\">pyplot<\/span> <span style=\"color: #008000;\">as<\/span> plt\n\nplt. <span style=\"color: #3366ff;\">scatter<\/span> (df.x, cooks[0])\nplt. <span style=\"color: #3366ff;\">xlabel<\/span> (' <span style=\"color: #008000;\">x<\/span> ')\nplt. <span style=\"color: #3366ff;\">ylabel<\/span> (' <span style=\"color: #008000;\">Cooks Distance<\/span> ')\nplt. <span style=\"color: #3366ff;\">show<\/span> ()<\/span><\/span><\/strong> <\/pre>\n<p><img decoding=\"async\" loading=\"lazy\" class=\"aligncenter wp-image-12869 \" src=\"https:\/\/statorials.org\/wp-content\/uploads\/2023\/08\/cuisinierspython1.png\" alt=\"Dist\u00e2ncia de Cook em Python\" width=\"420\" height=\"284\" srcset=\"\" sizes=\"auto, \"><\/p>\n<h3> <span style=\"color: #000000;\"><strong>Pensamentos finais<\/strong><\/span><\/h3>\n<p> <span style=\"color: #000000;\">\u00c9 importante notar que a dist\u00e2ncia de Cook deve ser usada para <em>identificar<\/em> observa\u00e7\u00f5es potencialmente influentes.<\/span> <span style=\"color: #000000;\">S\u00f3 porque uma observa\u00e7\u00e3o \u00e9 influente n\u00e3o significa que deva ser removida do conjunto de dados.<\/span><\/p>\n<p> <span style=\"color: #000000;\">Primeiro, voc\u00ea precisa verificar se a observa\u00e7\u00e3o n\u00e3o \u00e9 resultado de um erro de entrada de dados ou de outro evento estranho. Se for um valor leg\u00edtimo, voc\u00ea poder\u00e1 decidir se \u00e9 apropriado remov\u00ea-lo, deix\u00e1-lo como est\u00e1 ou simplesmente substitu\u00ed-lo por um valor alternativo como a mediana.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>A dist\u00e2ncia de Cook \u00e9 usada para identificar observa\u00e7\u00f5es influentes em um modelo de regress\u00e3o. A f\u00f3rmula para a dist\u00e2ncia de Cook \u00e9: d i = (r i 2 \/ p*MSE) * (h ii \/ (1-h ii ) 2 ) Ouro: ri \u00e9 o i- \u00e9simo res\u00edduo p \u00e9 o n\u00famero de coeficientes no modelo [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11],"tags":[],"class_list":["post-1314","post","type-post","status-publish","format-standard","hentry","category-guia"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v21.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Como calcular a dist\u00e2ncia de Cook em Python<\/title>\n<meta name=\"description\" content=\"Este tutorial explica como calcular a dist\u00e2ncia de Cook em Python, com um exemplo.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/statorials.org\/pt\/python-remoto-de-cozinha\/\" \/>\n<meta property=\"og:locale\" content=\"pt_PT\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Como calcular a dist\u00e2ncia de Cook em Python\" \/>\n<meta property=\"og:description\" content=\"Este tutorial explica como calcular a dist\u00e2ncia de Cook em Python, com um exemplo.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/statorials.org\/pt\/python-remoto-de-cozinha\/\" \/>\n<meta property=\"og:site_name\" content=\"Statorials\" \/>\n<meta property=\"article:published_time\" content=\"2023-07-26T22:01:06+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/statorials.org\/wp-content\/uploads\/2023\/08\/cuisinierspython1.png\" \/>\n<meta name=\"author\" content=\"Dr. benjamim anderson\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Escrito por\" \/>\n\t<meta name=\"twitter:data1\" content=\"Dr. benjamim anderson\" \/>\n\t<meta name=\"twitter:label2\" content=\"Tempo estimado de leitura\" \/>\n\t<meta name=\"twitter:data2\" content=\"3 minutos\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/statorials.org\/pt\/python-remoto-de-cozinha\/\",\"url\":\"https:\/\/statorials.org\/pt\/python-remoto-de-cozinha\/\",\"name\":\"Como calcular a dist\u00e2ncia de Cook em Python\",\"isPartOf\":{\"@id\":\"https:\/\/statorials.org\/pt\/#website\"},\"datePublished\":\"2023-07-26T22:01:06+00:00\",\"dateModified\":\"2023-07-26T22:01:06+00:00\",\"author\":{\"@id\":\"https:\/\/statorials.org\/pt\/#\/schema\/person\/e08f98e8db95e0aa9c310e1b27c9c666\"},\"description\":\"Este tutorial explica como calcular a dist\u00e2ncia de Cook em Python, com um exemplo.\",\"breadcrumb\":{\"@id\":\"https:\/\/statorials.org\/pt\/python-remoto-de-cozinha\/#breadcrumb\"},\"inLanguage\":\"pt-PT\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/statorials.org\/pt\/python-remoto-de-cozinha\/\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/statorials.org\/pt\/python-remoto-de-cozinha\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Lar\",\"item\":\"https:\/\/statorials.org\/pt\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Como calcular a dist\u00e2ncia de cook em python\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/statorials.org\/pt\/#website\",\"url\":\"https:\/\/statorials.org\/pt\/\",\"name\":\"Statorials\",\"description\":\"O seu guia para a literacia estat\u00edstica!\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/statorials.org\/pt\/?s={search_term_string}\"},\"query-input\":\"required name=search_term_string\"}],\"inLanguage\":\"pt-PT\"},{\"@type\":\"Person\",\"@id\":\"https:\/\/statorials.org\/pt\/#\/schema\/person\/e08f98e8db95e0aa9c310e1b27c9c666\",\"name\":\"Dr. benjamim anderson\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"pt-PT\",\"@id\":\"https:\/\/statorials.org\/pt\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/statorials.org\/pt\/wp-content\/uploads\/2023\/10\/Dr.-Benjamin-Anderson-96x96.jpg\",\"contentUrl\":\"https:\/\/statorials.org\/pt\/wp-content\/uploads\/2023\/10\/Dr.-Benjamin-Anderson-96x96.jpg\",\"caption\":\"Dr. benjamim anderson\"},\"description\":\"Ol\u00e1, sou Benjamin, um professor aposentado de estat\u00edstica que se tornou professor dedicado na Statorials. 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