使用ggplot2在不同图层中绘制多个ROC曲线

naco 发表于 Dev

177

做什么的

我正在尝试使用ggplot2在单个绘图上绘制多个ROC曲线。这是我走了多远：

ggroc2 <- function(columns, data = mtcars, classification = "am",
                   interval = 0.2, breaks = seq(0, 1, interval)){
  require(pROC)
  require(ggplot2)

  #The frame for the plot
  g <- ggplot() + geom_segment(aes(x = 0, y = 1, xend = 1,yend = 0)) +
    scale_x_reverse(name = "Specificity",limits = c(1,0), breaks = breaks, 
expand = c(0.001,0.001)) + 
    scale_y_continuous(name = "Sensitivity", limits = c(0,1), breaks = 
breaks, expand = c(0.001, 0.001)) +
    theme_classic() + coord_equal()

  #The loop to calculate ROC's and add them as new layers
  for(i in 1:length(columns)){
    croc <- roc(data[,classification], data[,columns[i]]) 
    plotx <- rev(croc$specificities)
    ploty <- rev(croc$sensitivities)
    g <- g + geom_step(aes(x=plotx, y=ploty))
  }

  g
}



#Sample graph
ggroc2(c("mpg", "disp", "drat", "wt"))

问题在于仅columns绘制了列表中的最后一个参数。aes()阅读该问题的答案后，我发现该问题必须与懒惰评估有关。该示例使用geom_segment()，并且aes()完全删除后解决了问题。它对我不起作用，因为我需要以某种方式映射数据。当我移开aes()这里时，什么也没画。如何解决geom_依赖于的惰性评估问题aes()？

马可·桑德里（Marco Sandri）

这是您的代码的有效版本。
最终的图形结果不是很好，应该加以改进。

ggroc2 <- function(columns, data = mtcars, classification = "am",
                   interval = 0.2, breaks = seq(0, 1, interval)){
  require(pROC)
  require(ggplot2)

  #The frame for the plot
  g <- ggplot() + geom_segment(aes(x = 0, y = 1, xend = 1,yend = 0)) +
    scale_x_reverse(name = "Specificity",limits = c(1,0), breaks = breaks, 
expand = c(0.001,0.001)) + 
    scale_y_continuous(name = "Sensitivity", limits = c(0,1), breaks = 
breaks, expand = c(0.001, 0.001)) +
    theme_classic() + coord_equal()

  #The loop to calculate ROC's and add them as new layers
  cols <- palette()
  for(i in 1:length(columns)){
    croc <- roc(data[,classification], data[,columns[i]]) 
    sens_spec <- data.frame(spec=rev(croc$specificities),
                            sens=rev(croc$sensitivities))
    g <- g + geom_step(aes(x=spec, y=sens), data=sens_spec, col=cols[i], lwd=1)
  }
  g
}

#Sample graph
ggroc2(c("mpg", "disp", "drat", "wt"))