{"id":632,"date":"2011-11-10T12:26:10","date_gmt":"2011-11-10T11:26:10","guid":{"rendered":"https:\/\/abcdr.guyader.pro\/?p=632"},"modified":"2018-04-07T23:59:24","modified_gmt":"2018-04-07T22:59:24","slug":"comment-utiliser-la-fonction-by-de-r","status":"publish","type":"post","link":"https:\/\/thinkr.fr\/abcdr\/comment-utiliser-la-fonction-by-de-r\/","title":{"rendered":"Comment utiliser la fonction by de R ?"},"content":{"rendered":"

La fonction \u00ab\u00a0by\u00a0\u00bb est tr\u00e8s int\u00e9ressante pour \u00e9viter des boucles \u00ab\u00a0for\u00a0\u00bb et ainsi optimiser le code<\/p>\n

data(iris)
summary(iris)
by(iris[,-5],iris[,5],mean)
\u00a0<\/p><\/code><\/pre>\n
ou encore quant vous voulez effectuer une fonction qui n’est pas d\u00e9finie.<\/p>\n

 by(iris[,-5],iris[,5],function(ob){
#mettez ici l'op\u00e9ration que vous voulez faire sur le subset
return()
})
\u00a0 
 <\/code><\/pre>\n
Le probl\u00e8me peut \u00eatre que by retourne une liste et que l’on voudrait avoir un tableau de donn\u00e9es. C’est ce que fait la fonction do.call, elle prend une liste et effectue une action dessus (ici rbind).<\/p>\n

 
data(iris)
summary(iris)
do.call(rbind,by(iris[,-5],iris[,5],mean) )

 <\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"
La fonction \u00ab\u00a0by\u00a0\u00bb est tr\u00e8s int\u00e9ressante pour \u00e9viter des boucles \u00ab\u00a0for\u00a0\u00bb et ainsi optimiser le code data(iris)summary(iris)by(iris[,-5],iris[,5],mean)\u00a0 ou encore quant vous voulez effectuer une fonction qui n’est pas d\u00e9finie. by(iris[,-5],iris[,5],function(ob){#mettez ici l’op\u00e9ration que vous voulez faire sur le subsetreturn()})\u00a0 Le probl\u00e8me peut \u00eatre que by retourne une liste et que l’on voudrait avoir un tableau de donn\u00e9es. C’est ce que fait la fonction do.call, elle prend une liste et effectue une action dessus (ici rbind). data(iris)summary(iris)do.call(rbind,by(iris[,-5],iris[,5],mean) )Read More →<\/a><\/p>\n","protected":false},"author":7,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"content-type":"","rop_custom_images_group":[],"rop_custom_messages_group":[],"rop_publish_now":"initial","rop_publish_now_accounts":{"twitter_399453572_399453572":""},"rop_publish_now_history":[],"rop_publish_now_status":"pending","jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[23],"tags":[],"class_list":{"0":"entry","1":"post","2":"publish","3":"author-guillaume","4":"post-632","6":"format-standard","7":"category-transformation-de-donnees"},"acf":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p9O7Sx-ac","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/thinkr.fr\/abcdr\/wp-json\/wp\/v2\/posts\/632","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/thinkr.fr\/abcdr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/thinkr.fr\/abcdr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/thinkr.fr\/abcdr\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"https:\/\/thinkr.fr\/abcdr\/wp-json\/wp\/v2\/comments?post=632"}],"version-history":[{"count":2,"href":"https:\/\/thinkr.fr\/abcdr\/wp-json\/wp\/v2\/posts\/632\/revisions"}],"predecessor-version":[{"id":4112,"href":"https:\/\/thinkr.fr\/abcdr\/wp-json\/wp\/v2\/posts\/632\/revisions\/4112"}],"wp:attachment":[{"href":"https:\/\/thinkr.fr\/abcdr\/wp-json\/wp\/v2\/media?parent=632"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/thinkr.fr\/abcdr\/wp-json\/wp\/v2\/categories?post=632"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/thinkr.fr\/abcdr\/wp-json\/wp\/v2\/tags?post=632"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}