Ggplot legend shows transparency and fill color

Question

I draw two translucent ribbons together. Using the code below, without the scale_fill_manual part, I get basically what I want, with a legend called "red" and the inscriptions blue and red . Adding the scale_fill_manual part allows me to name the legend and its entries what I want, but I lose the transparency of the colored rectangles in the legend.

 x=1:10 y1=1:10 y2=2:11 y3=10:1 y4=9:0 dt=data.frame(x,y1,y2,y3,y4) library(ggplot2) ggplot(dt)+ geom_ribbon(aes(x=x,ymin=y1,ymax=y2,fill='red'), alpha=0.4,)+ geom_ribbon(aes(x=x,ymin=y3,ymax=y4,fill='blue'), alpha=0.5)+ scale_fill_manual(name='legendname', values=c('red','blue'), labels=c('one','two')) 

sessionInfo () output

 R version 2.15.2 (2012-10-26) Platform: x86_64-apple-darwin9.8.0/x86_64 (64-bit) locale: [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8 attached base packages: [1] stats graphics grDevices utils datasets methods base other attached packages: [1] scales_0.2.3 ggplot2_0.9.3 plyr_1.8 reshape2_1.2.2 loaded via a namespace (and not attached): [1] colorspace_1.2-0 dichromat_1.2-4 digest_0.6.0 grid_2.15.2 gtable_0.1.2 labeling_0.1 [7] MASS_7.3-22 munsell_0.4 proto_0.3-10 RColorBrewer_1.0-5 rstudio_0.97.248 stringr_0.6.2 [13] tools_2.15.2 

There are many solutions for such problems ( Set up a legend in ggplot , https://stats.stackexchange.com/questions/5007/how-can-i-change-the-title-of-a-legend-in-ggplot2 , etc. .d.), but I can not find anything that specifically relates to this.

Thank you in advance

Answer 1

You can redefine aesthetics in a legend by adding:

 + guides(fill = guide_legend(override.aes= list(alpha = 0.4))) 

to your ggplot call.

But, like most things in ggplot, it may be easier to arrange your data so that unnecessary calls to geom_ribbon :

 dt1 <- data.frame(x = c(x,x), ymin = c(y1,y3), ymax = c(y2,y4), grp = rep(c('red','blue'),each = 10)) ggplot(data = dt1,aes(x = x,ymin = ymin, ymax = ymax,fill = grp)) + geom_ribbon(alpha = 0.4) + scale_fill_manual(name = "legendname", values = c('red','blue'), labels = c('one','two'))