{"id":559,"date":"2022-02-03T15:37:12","date_gmt":"2022-02-03T14:37:12","guid":{"rendered":"https:\/\/alessandromasciadri.com\/?p=559"},"modified":"2022-02-03T15:40:58","modified_gmt":"2022-02-03T14:40:58","slug":"come-contare-le-occorrenze-di-valori-in-un-dataframe-pandas","status":"publish","type":"post","link":"https:\/\/alessandromasciadri.com\/come-contare-le-occorrenze-di-valori-in-un-dataframe-pandas\/","title":{"rendered":"Come contare le occorrenze di valori in un DataFrame Pandas"},"content":{"rendered":"\t\t<div data-akihiro-type=\"ama-post\" data-akihiro-id=\"559\" class=\"akihiro akihiro-559\" data-akihiro-post-type=\"post\">\n\t\t\t\t\t\t<section class=\"akihiro-section akihiro-top-section akihiro-element akihiro-element-cb6c1c4 akihiro-section-boxed akihiro-section-height-default akihiro-section-height-default\" data-id=\"cb6c1c4\" data-element_type=\"section\" data-e-type=\"section\">\n\t\t\t\t\t\t<div class=\"akihiro-container akihiro-column-gap-default\">\n\t\t\t\t\t<div class=\"akihiro-column akihiro-col-100 akihiro-top-column akihiro-element akihiro-element-223bd21\" data-id=\"223bd21\" data-element_type=\"column\" data-e-type=\"column\">\n\t\t\t<div class=\"akihiro-widget-wrap akihiro-element-populated\">\n\t\t\t\t\t\t<div class=\"akihiro-element akihiro-element-6297651 akihiro-widget akihiro-widget-text-editor\" data-id=\"6297651\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"akihiro-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>Se ci troviamo nella circostanza di dover contare\u00a0 le occorrenze di valori presenti in un DataFrame Pandas, ossia quante volte questi valori vengono ripetuti all&#8217;interno del DataFrame, possiamo ricorrere all&#8217;uso della funzione value_counts().<\/p><p>Ipotiziamo di avere il seguente DataFrame:<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"akihiro-element akihiro-element-c2df314 akihiro-widget akihiro-widget-code-highlight\" data-id=\"c2df314\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"code-highlight.default\">\n\t\t\t\t<div class=\"akihiro-widget-container\">\n\t\t\t\t\t\t\t<div class=\"prismjs-okaidia copy-to-clipboard \">\n\t\t\t<pre data-line=\"\" class=\"highlight-height language-python line-numbers\">\n\t\t\t\t<code readonly=\"true\" class=\"language-python\">\n\t\t\t\t\t<xmp>import pandas as pd\ndf = pd.DataFrame(['bmw','audi','bmw','ford','bmw','audi','ford','ford','ford','ford','audi','bmw','bmw','bmw','bmw',], columns=['auto'])\nprint(df)<\/xmp>\n\t\t\t\t<\/code>\n\t\t\t<\/pre>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"akihiro-element akihiro-element-8a57c0a akihiro-widget akihiro-widget-heading\" data-id=\"8a57c0a\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"akihiro-widget-container\">\n\t\t\t\t\t<span class=\"akihiro-heading-title akihiro-size-default\">Output:<\/span>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"akihiro-element akihiro-element-acf7d65 akihiro-widget akihiro-widget-code-highlight\" data-id=\"acf7d65\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"code-highlight.default\">\n\t\t\t\t<div class=\"akihiro-widget-container\">\n\t\t\t\t\t\t\t<div class=\"prismjs-okaidia  \">\n\t\t\t<pre data-line=\"\" class=\"highlight-height language-bash \">\n\t\t\t\t<code readonly=\"true\" class=\"language-bash\">\n\t\t\t\t\t<xmp>_   auto\r\n0    bmw\r\n1   audi\r\n2    bmw\r\n3   ford\r\n4    bmw\r\n5   audi\r\n6   ford\r\n7   ford\r\n8   ford\r\n9   ford\r\n10  audi\r\n11   bmw\r\n12   bmw\r\n13   bmw\r\n14   bmw<\/xmp>\n\t\t\t\t<\/code>\n\t\t\t<\/pre>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"akihiro-element akihiro-element-0093822 akihiro-widget akihiro-widget-text-editor\" data-id=\"0093822\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"akihiro-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>Possiamo a questo punto utilizzare la funzione value_counts() per contare le occorrenze all&#8217;interno del DataFrame.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"akihiro-element akihiro-element-37060ce akihiro-widget akihiro-widget-code-highlight\" data-id=\"37060ce\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"code-highlight.default\">\n\t\t\t\t<div class=\"akihiro-widget-container\">\n\t\t\t\t\t\t\t<div class=\"prismjs-okaidia copy-to-clipboard \">\n\t\t\t<pre data-line=\"\" class=\"highlight-height language-python line-numbers\">\n\t\t\t\t<code readonly=\"true\" class=\"language-python\">\n\t\t\t\t\t<xmp>print(df.value_counts())<\/xmp>\n\t\t\t\t<\/code>\n\t\t\t<\/pre>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"akihiro-element akihiro-element-eff2229 akihiro-widget akihiro-widget-heading\" data-id=\"eff2229\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"akihiro-widget-container\">\n\t\t\t\t\t<span class=\"akihiro-heading-title akihiro-size-default\">Output:<\/span>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"akihiro-element akihiro-element-6c5a291 akihiro-widget akihiro-widget-code-highlight\" data-id=\"6c5a291\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"code-highlight.default\">\n\t\t\t\t<div class=\"akihiro-widget-container\">\n\t\t\t\t\t\t\t<div class=\"prismjs-okaidia  \">\n\t\t\t<pre data-line=\"\" class=\"highlight-height language-bash \">\n\t\t\t\t<code readonly=\"true\" class=\"language-bash\">\n\t\t\t\t\t<xmp>auto\r\nbmw     7\r\nford    5\r\naudi    3\r\ndtype: int64<\/xmp>\n\t\t\t\t<\/code>\n\t\t\t<\/pre>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"akihiro-element akihiro-element-ab18a9d akihiro-widget akihiro-widget-heading\" data-id=\"ab18a9d\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"akihiro-widget-container\">\n\t\t\t\t\t<h2 class=\"akihiro-heading-title akihiro-size-default\">Contare le occorrenze in un DataFrame memorizzandole in un Dizionario<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"akihiro-element akihiro-element-8ccbc06 akihiro-widget akihiro-widget-text-editor\" data-id=\"8ccbc06\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"akihiro-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>In questo caso, vogliamo contare le occorrenze presenti nel DataFrame e vogliamo organizzare il risultato in un dizionario. Per fare ci\u00f2 dobbiamo utilizzare la funzione to_dict() la quale per\u00f2 pu\u00f2 essere applicata ad una serie, pertanto dobbiamo eseguire il counting su una singola colonna del DataFrame.<\/p><p>Il codice \u00e8 il seguente:<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"akihiro-element akihiro-element-2f5b053 akihiro-widget akihiro-widget-code-highlight\" data-id=\"2f5b053\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"code-highlight.default\">\n\t\t\t\t<div class=\"akihiro-widget-container\">\n\t\t\t\t\t\t\t<div class=\"prismjs-okaidia copy-to-clipboard \">\n\t\t\t<pre data-line=\"\" class=\"highlight-height language-python line-numbers\">\n\t\t\t\t<code readonly=\"true\" class=\"language-python\">\n\t\t\t\t\t<xmp>counts = df['auto'].value_counts().to_dict()<\/xmp>\n\t\t\t\t<\/code>\n\t\t\t<\/pre>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"akihiro-element akihiro-element-ea85904 akihiro-widget akihiro-widget-heading\" data-id=\"ea85904\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"heading.default\">\n\t\t\t\t<div class=\"akihiro-widget-container\">\n\t\t\t\t\t<span class=\"akihiro-heading-title akihiro-size-default\">Output:<\/span>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<div class=\"akihiro-element akihiro-element-538c459 akihiro-widget akihiro-widget-code-highlight\" data-id=\"538c459\" data-element_type=\"widget\" data-e-type=\"widget\" data-widget_type=\"code-highlight.default\">\n\t\t\t\t<div class=\"akihiro-widget-container\">\n\t\t\t\t\t\t\t<div class=\"prismjs-okaidia  \">\n\t\t\t<pre data-line=\"\" class=\"highlight-height language-bash \">\n\t\t\t\t<code readonly=\"true\" class=\"language-bash\">\n\t\t\t\t\t<xmp>{'bmw': 7, 'ford': 5, 'audi': 3}<\/xmp>\n\t\t\t\t<\/code>\n\t\t\t<\/pre>\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>Se ci troviamo nella circostanza di dover contare\u00a0 le occorrenze di valori presenti in un DataFrame Pandas, ossia quante volte questi valori vengono ripetuti all&#8217;interno del DataFrame, possiamo ricorrere all&#8217;uso della funzione value_counts(). Ipotiziamo di avere il seguente DataFrame: import pandas as pd df = pd.DataFrame([&#8216;bmw&#8217;,&#8217;audi&#8217;,&#8217;bmw&#8217;,&#8217;ford&#8217;,&#8217;bmw&#8217;,&#8217;audi&#8217;,&#8217;ford&#8217;,&#8217;ford&#8217;,&#8217;ford&#8217;,&#8217;ford&#8217;,&#8217;audi&#8217;,&#8217;bmw&#8217;,&#8217;bmw&#8217;,&#8217;bmw&#8217;,&#8217;bmw&#8217;,], columns=[&#8216;auto&#8217;]) print(df) Output: _ auto 0 bmw 1 audi [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[24,12],"class_list":["post-559","post","type-post","status-publish","format-standard","hentry","category-programmazione","tag-pandas","tag-python"],"_links":{"self":[{"href":"https:\/\/alessandromasciadri.com\/ama-json\/wp\/v2\/posts\/559","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/alessandromasciadri.com\/ama-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/alessandromasciadri.com\/ama-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/alessandromasciadri.com\/ama-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/alessandromasciadri.com\/ama-json\/wp\/v2\/comments?post=559"}],"version-history":[{"count":4,"href":"https:\/\/alessandromasciadri.com\/ama-json\/wp\/v2\/posts\/559\/revisions"}],"predecessor-version":[{"id":563,"href":"https:\/\/alessandromasciadri.com\/ama-json\/wp\/v2\/posts\/559\/revisions\/563"}],"wp:attachment":[{"href":"https:\/\/alessandromasciadri.com\/ama-json\/wp\/v2\/media?parent=559"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/alessandromasciadri.com\/ama-json\/wp\/v2\/categories?post=559"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/alessandromasciadri.com\/ama-json\/wp\/v2\/tags?post=559"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}