R语言的点图dot plot

点图简介

点图又叫Cleveland dot plot,克利夫兰点图。可以在水平线上绘制大量的点，更好的表示点之间的关系。强调数据的排序展示以及数据之间的差距。点图一般是横向展示，所以y轴为类别型变量，x轴为需要展示的数据值。

dotchart函数

dotchart(x, labels = NULL, groups = NULL, gdata = NULL,
         ann = par("ann"), xaxt = par("xaxt"), frame.plot = TRUE, log = "",
         cex = par("cex"), pt.cex = cex,
         pch = 21, gpch = 21, bg = par("bg"),
         color = par("fg"), gcolor = par("fg"), lcolor = "gray",
         xlim = range(x[is.finite(x)]),
         main = NULL, xlab = NULL, ylab = NULL, ...)

R语言的base包里面自带的dotchart函数可以绘制点图。
上面简介中的例子copy自dotchart的函数帮助文档。

dotchart(VADeaths, main = "Death Rates in Virginia - 1940")

数据是1940年每1000人的死亡率。数据按照年龄段来区分，并且按照地方，男女性分组。

> VADeaths
      Rural Male Rural Female Urban Male Urban Female
50-54       11.7          8.7       15.4          8.4
55-59       18.1         11.7       24.3         13.6
60-64       26.9         20.3       37.0         19.3
65-69       41.0         30.9       54.6         35.1
70-74       66.0         54.3       71.1         50.0

dot 比较图

我想比较特定地方的男女死亡率的比较。这样的话，数据需要处理。下面的code处理的比较麻烦。但是达到了我要的效果。

ruralDFMale <- data.frame(rownames(VADeaths),VADeaths[,1], c("Male","Male","Male","Male","Male"))
names(ruralDFMale ) <- c("AgeGroup", "DeathRate","Gender" )

ruralDFFeMale <- data.frame(rownames(VADeaths),VADeaths[,2], c("Female","Female","Female","Female","Female"))
names(ruralDFFeMale) <- c("AgeGroup", "DeathRate","Gender" )

ruralDF <- rbind(ruralDFMale, ruralDFFeMale)

colorFun <- function(gender) {
    colorVec <- vector()
    for(g in gender) {
        if(g == "Female") {
            colorVec <- c(colorVec, "Red")
        } else {
           colorVec <- c(colorVec, "Blue")
        }
    }

    colorVec 
}

dotchart(ruralDF$DeathRate, main = "Death Rates in Virginia - 1940", groups=ruralDF$AgeGroup,color=colorFun(ruralDF$Gender))

处理过后的数据

> ruralDF
       AgeGroup DeathRate Gender
50-54     50-54      11.7   Male
55-59     55-59      18.1   Male
60-64     60-64      26.9   Male
65-69     65-69      41.0   Male
70-74     70-74      66.0   Male
50-541    50-54       8.7 Female
55-591    55-59      11.7 Female
60-641    60-64      20.3 Female
65-691    65-69      30.9 Female
70-741    70-74      54.3 Female

图中的红色为女性，蓝色为男性。结果符合一般的常识，女性的寿命高于男性。所以同一年龄段的女性死亡率比男性低。