我试图用ggplot2在单个图上绘制多条ROC曲线。这是我有多远:
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"))
问题是只会绘制columns
列表中的最后一个参数。我发现在阅读the answer to this question后问题必须与aes()
和懒惰评估相关。该示例使用了geom_segment()
,并且在完全删除aes()
后问题得以解决。它对我不起作用,因为我需要以某种方式映射数据。当我在此处删除aes()
时,不会绘制任何内容。如何解决依赖于geom_
的{{1}}中的惰性评估问题?