ggplot2绘图中修改图例的标题

library(ggplot2)
bp <- ggplot(data=PlantGrowth, aes(x=group, y=weight, fill=group)) + geom_boxplot()
bp       ## 显示绘图结果

bp + scale_fill_discrete(name="Experimental\nCondition")  ## 修改图例标题的名称