ggplot2使用scale_color_identity（）更改条形图中的颜色

Question

I'm using the workaround to remove diagonal lines from a ggplot legend: https://groups.google.com/forum/?fromgroups=#!topic/ggplot2/vJnF9_HBqx4

With the following data, how do I change the colours of the groups?

# Create data #

a<-as.data.frame(c(1,1,1,2,2))
b<-as.data.frame(c("A","A","B","B","A"))
c<-as.data.frame(c(20,20,60,50,50))
a<-cbind(a,b,c)
colnames(a)<-c("X","Gp","Y")

# Plot #

ggplot(a, aes(x=X, y=Y,fill=Gp)) + 
  geom_bar(stat = "identity", aes(colour = "black")) + 
  scale_color_identity() + 
  theme(legend.key = element_rect(colour = "black", size = 1))

I have tried changing the following elements :

scale_color_identity(values=c("red","yellow"))

geom_bar(stat = "identity", aes(colour = c("red","yellow")))

geom_bar(stat = "identity", aes(colour = "black"), fill=c("red","yellow"))

but each produces an error.

Answer 1

Try this. The guides call let's you pick which scale to not have a legend. And, you can set the outline colour without aes().

EDIT after comment about diagonal line in legend

Based on this SO question remove diagonal line in legend , you can added the guides(fill etc. call to remove the diagonal.

ggplot(a, aes(x=X, y=Y,fill=Gp)) + 
  geom_bar(stat = "identity", colour = "black") + 
  scale_fill_manual(values = c("red","yellow")) +
  guides(fill = guide_legend(override.aes = list(colour = NULL))) +
  guides(colour = FALSE)

Answer 2

You can also call geom_bar twice. Once for the legend, and without the color argument, and once with the color argument but suppressing the legend

 ggplot(a, aes(x=X, y=Y,fill=Gp)) + 
       geom_bar(stat = "identity", color = 'black', show_guide = F) +
       geom_bar(stat = 'identity') + 
       scale_fill_manual(values = c('red', 'yellow') )