图例中的线型不正确，R中的ggplot2不正确

Question

I have created a ggplot2 plot in R where a line is accompanied by a shaded confidence interval. However, the legend shows the wrong colour and symbol. Using scale_size_manual does not seem to correct the issue.

The plot:

The input data:

my_example_data <- data.frame(Price = c(5,0,-5), Consumption = c(20,0,-20), Lower = c(17,-3,-21), Upper = c(21, 2, 23))
my_example_data.melt <- melt(my_example_data, id = "Price")

  Price    variable value
1     5 Consumption    20
2     0 Consumption     0
3    -5 Consumption   -20
4     5       Lower    17
5     0       Lower    -3
6    -5       Lower   -21
7     5       Upper    21
8     0       Upper     2
9    -5       Upper    23

The code to create the plot:

ggplot(subset(my_example_data.melt, variable == "Consumption"), aes(Price,value,fill='Mean response'), linetype=1) +
geom_line(colour="#000000")  +
coord_cartesian(xlim = c(-100, 100),ylim = c(-0.75, 1)) +
geom_ribbon(aes(ymin = subset(my_example_data.melt, variable == "Lower")$value, ymax = subset(my_example_data.melt, variable == "Upper")$value,fill = 'SD of response'),alpha=0.3, colour=NA) +
xlab("Change in relative price [Δ€]") +
ylab("Change in consumption [MW]") +
theme(legend.position="bottom", legend.direction="horizontal") +
xlab("Change in relative price [Δ€]") +
ylab("Change in consumption [MW]") +
scale_fill_discrete("")

Is there a manual override option for changing the linetypes and colour for the plot and legend without having to add additional information to the melted dataframe?

Answer 1

You will find this much easier not using the melted data.

Also quoting from Remove extra legends in ggplot2 ,

Aesthetics can be set or mapped within a ggplot call.

• An aesthetic defined within aes(...) is mapped from the data, and a legend created.
• An aesthetic may also be set to a single value, by defining it outside aes().

Therefore something like

 ggplot(my_example_data,aes(x=Price)) + 
   geom_ribbon(aes(ymin=Lower,ymax=Upper),fill='blue',alpha=0.5) +  
   geom_line(aes(y=Consumption)) 

or perhaps If you really wanted a legend, you could use scale_identity

ggplot(my_example_data,aes(x=Price)) + 
  geom_ribbon(aes(ymin=Lower,ymax=Upper,fill='blue'), alpha=0.5) + 
  geom_line(aes(y=Consumption)) + 
  scale_fill_identity(guide='legend', name = 'Your name', label = 'whatever')