ggplot2: how to remove slash from geom_density legend

Question

I'm trying to plot some overlapping density plots in ggplot2. I'm running into a problem where I cannot remove the diagonal slash from the legend. I have tried using scale_fill_manual() and legend.key as well as the hack from R Cookbook, but I cant seem to get it right.

data(iris)
iris=iris
cols=brewer.pal(3,"Set1")

ggplot(iris) + 
    geom_density(position="identity",aes(x=iris$Sepal.Length,fill=cols[1]),
        colour="black",alpha=.5) +
    geom_density(position="identity",aes(x=iris$Sepal.Width,fill=cols[2]),
        colour="black",alpha=.5)+  
    theme_bw() +
    scale_fill_identity(guide="legend",labels=c("Sepal Width","Sepal Length"))+
    xlab("X axis") +
    theme(panel.background=element_blank(),
        legend.title=element_blank(),
        legend.key = element_rect(),
        legend.background = element_blank(),
        legend.justification=c(1,0), 
        legend.position=c(.75,.5),
        panel.grid.major = element_blank(),
        panel.grid.minor = element_blank(),
        panel.border = element_blank(),
        panel.background = element_blank())

What can I do to solve this?

Answer 1

Try this:

+ guides(fill = guide_legend(override.aes = list(colour = NULL)))

although that removes the black outline as well...which can be added back in by change the theme to:

legend.key = element_rect(colour = "black")

I completely forgot to add this important note: do not specify aesthetics via x=iris$Sepal.Length using the $ operator! That is not the intended way to use aes() and it will lead to errors and unexpected problems down the road.