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Dotted line in ggplot legend

I want to set the linetype of my legend.

My details:

  VisitMonth VisitYear CaixaForum MNAC   FirstDay
  1:         01      2007         NA 7125 2007-01-01
  2:         02      2007         NA 5345 2007-02-01
  3:         03      2007         NA 4996 2007-03-01
  4:         04      2007         NA 5476 2007-04-01
  5:         05      2007         NA 6160 2007-05-01
 ---                                                
 98:         02      2015      17903 2360 2015-02-01
 99:         03      2015      30400 2930 2015-03-01
100:         04      2015      25422 3088 2015-04-01
101:         05      2015      10787 2130 2015-05-01
102:         06      2015       3679 2047 2015-06-01

I want to build a CaixaForum time series and MNAC columns. I have some code:

ggplot(data = MUSEUMS, aes(x = FirstDay, y = MNAC)) + 
  geom_line(size=0.75, aes(x = FirstDay, y = MNAC, colour = "MNAC")) + 
  geom_line(size=0.75, aes(y = CaixaForum, colour = "CaixaForum"), linetype = "dashed") + 
  labs(title = "", x = "", y = "Monthly Visitors") +  theme_bw() + 
  theme(legend.title = element_text(size=16, face="bold"),  legend.direction = "horizontal",
        legend.position=c(0.5, 1.05), text = element_text(size=20)) + 
  scale_colour_manual(name="Legend",values=c(MNAC="black", CaixaForum="black"))

As you can see, you cannot distinguish between the two types of lines in the legend:

enter image description here

How can I fix it?

I have coded other answers on stackoverflow, but they didn't work.

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2 answers


You can just switch to use in two point layers linetype

instead color

, since you are not actually using color

for anything in your graphics.

It will look like this:

ggplot(data = MUSEUMS, aes(x = FirstDay, y = MNAC)) + 
    geom_line(size=0.75, aes(x = FirstDay, y = MNAC, linetype = "MNAC")) + 
    geom_line(size=0.75, aes(y = CaixaForum, linetype = "CaixaForum")) + 
    labs(title = "", x = "", y = "Monthly Visitors") +  theme_bw() + 
    theme(legend.title = element_text(size=16, face="bold"),  legend.direction = "horizontal",
            legend.position=c(0.5, 1.05), text = element_text(size=20)) + 
    scale_linetype_manual(name="Legend",values=c(MNAC="solid", CaixaForum="dashed"))


If you really want to use an approach that is currently using for any reason, you can get the desired line using override.aes

in guide_legend

adding the following line to your chart:

guides(color = guide_legend(override.aes = list(linetype = c("solid", "dashed"))))
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I created some random data to demonstrate the solution ...



library(reshape2)
df <- data.frame(a=rnorm(10), b=rnorm(10), x=1:10, other_data=rnorm(10))
mdf <- melt(df, id.vars='x', measure.vars=c('a','b'))
ggplot(mdf, aes(x, value, linetype=variable)) + geom_line()
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