是否可以通过美学来改变绘图的颜色渐变?我正在使用类似下面提供的代码生成一个图表,并发现在某些情况下很难区分各个组之间的差异。例如,在下面的图表中,如果我可以让A组点使用白蓝渐变,B组点使用白红渐变,那么区分结果将更容易。
data <- data.frame(x=c(1,2,3,4,5,6,1,2,3,4,5,6),
y=c(1,2,3,4,5,6,1,2,3,4,5,6), grp=c(rep("A",6),rep("B",6)),
dt=c("2010-06-30","2010-05-31","2010-04-30",
"2010-03-31","2010-02-26","2010-01-29","2010-06-30",
"2010-05-31","2010-04-30",
"2010-03-31","2010-02-26","2010-01-29"))
p <- ggplot(data, aes(x,y,color=as.integer(as.Date(data$dt)))) +
geom_jitter(size=4, alpha=0.75, aes(shape=grp)) +
scale_colour_gradient(limits=as.integer(as.Date(c("2010-01-29","2010-06-30"))),
low="white", high="blue") +
scale_shape_discrete(name="") +
opts(legend.position="none")
print(p)