{"id":412,"date":"2014-01-01T22:15:20","date_gmt":"2014-01-02T03:15:20","guid":{"rendered":"http:\/\/homepages.uc.edu\/~yaozo\/wordpress\/?p=412"},"modified":"2014-01-01T22:15:20","modified_gmt":"2014-01-02T03:15:20","slug":"ggplot2-plotting-two-or-more-overlapping-density-plots-on-the-same-graph","status":"publish","type":"post","link":"https:\/\/zhuoyao.net\/index.php\/2014\/01\/01\/ggplot2-plotting-two-or-more-overlapping-density-plots-on-the-same-graph\/","title":{"rendered":"ggplot2: Plotting two or more overlapping density plots on the same graph"},"content":{"rendered":"
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One R Tip A Day<\/a>\u00a0uses a custom R function to plot two or more overlapping density plots on the same graph.<\/p>\n

\"http:\/\/learnr.files.wordpress.com\/2009\/03\/3densities.gif?w=400&h=400\"<\/div>\n

The same can be very easily accomplished in\u00a0ggplot2<\/a>.<\/p>\n

 <\/p>\n\n\n\n
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> library(ggplot2)<\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
Create dummy dataframe:<\/p>\n\n\n\n
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> df <- data.frame(x = rnorm(1000, 0, 1), y = rnorm(1000,\n     0, 2), z = rnorm(1000, 2, 1.5))<\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\u201cMelt\u201d data:<\/p>\n\n\n\n
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> df.m <- melt(df)<\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
Default plot:<\/p>\n\n\n\n
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> ggplot(df.m) + geom_freqpoly(aes(x = value,\n     y = ..density.., colour = variable))<\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\"http:\/\/learnr.files.wordpress.com\/2009\/03\/density3.png?w=416&h=415\"<\/div>\n
Default plot + few formatting adjustments:<\/p>\n\n\n\n
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> ggplot(df.m) + geom_freqpoly(aes(x = value,\n     y = ..density.., colour = variable)) +\n     labs(x = NULL) + opts(legend.position = \"none\") +\n     opts(title = \"Frequency Polygons (based on binned counts)\")<\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\"http:\/\/learnr.files.wordpress.com\/2009\/03\/density11.png?w=416&h=415\"<\/div>\n
Update:<\/strong>\u00a0Hadley kindly points out that the above plots are frequency polygons. I have updated the post with a \u201creal\u201d density plot.<\/p>\n\n\n\n
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> ggplot(df.m) + geom_density(aes(x = value,\n     colour = variable)) + labs(x = NULL) +\n     opts(legend.position = \"none\") + opts(title = \"Densities from a kernel density estimator\")<\/pre>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\"http:\/\/learnr.files.wordpress.com\/2009\/03\/density2.png?w=416&h=415\"<\/div>\n
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<\/div>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
One R Tip A Day\u00a0uses a custom R function to plot two or more overlapping density plots on the same graph. The same can be… <\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[20],"tags":[],"class_list":["post-412","post","type-post","status-publish","format-standard","hentry","category-r"],"_links":{"self":[{"href":"https:\/\/zhuoyao.net\/index.php\/wp-json\/wp\/v2\/posts\/412","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/zhuoyao.net\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/zhuoyao.net\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/zhuoyao.net\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/zhuoyao.net\/index.php\/wp-json\/wp\/v2\/comments?post=412"}],"version-history":[{"count":0,"href":"https:\/\/zhuoyao.net\/index.php\/wp-json\/wp\/v2\/posts\/412\/revisions"}],"wp:attachment":[{"href":"https:\/\/zhuoyao.net\/index.php\/wp-json\/wp\/v2\/media?parent=412"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/zhuoyao.net\/index.php\/wp-json\/wp\/v2\/categories?post=412"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/zhuoyao.net\/index.php\/wp-json\/wp\/v2\/tags?post=412"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}