CODEWITHSUNDEEP
rggplot2legend
Dekike
Dekike

Reputation: 1284

Why my `legend.text` and colour is not assigned properly in a second legend using `scale_linetype_manual` and `guides`?

The plot below is to create a ggplot in which I show the relationship between two variables according to the raw data (points) and according to my model (dashed lines, each one for different ID).

Plot_a <- ggplot(Todo.6min, aes(x=VeDBA.V13AP, y=VeDBA.X16, colour=ID)) + 
  geom_point(size=1.5,alpha=0.2) +
  geom_line(aes(y=predict(mod3.6min,df.6min), group=ID), size=3, alpha=0.6, linetype="dashed") +
  geom_abline(aes(slope=1,intercept=0),linetype="dashed",color="grey52",size=1.5) +
  theme_bw() + 
  theme(legend.text=element_text(size=18),
        legend.title = element_text(size=19, face = "bold"),
        legend.key=element_blank()) +
  guides(color=guide_legend(override.aes=list(fill=NA)))

Plot_a

enter image description here

Then, I add some extra lines from a different model and I colour those lines using a palette of colours from RColorBrewer. As you can see, I include a second legend relative to this second model in which appears as legend.title "n.V13AP" and as legend.text "Low","Medium" and "High". The dark red colour should correspond to the nV13AP level High, and the less intense red colour should correspond to the nV13AP level Low.

line_colors <- RColorBrewer::brewer.pal(7, "Reds")[c(2,4,6)]
line_colors

Plot_a.2 <- Plot_a +
  geom_line(aes(y=predict(mod3.6min_gls,df.6min_low.n), linetype = "Low"), color = line_colors[1], size=1.5, alpha=1) +
  geom_line(aes(y=predict(mod3.6min_gls,df.6min_medium.n), linetype = "Medium"), color = line_colors[2], size=1.5, alpha=1) +
  geom_line(aes(y=predict(mod3.6min_gls,df.6min_high.n), linetype = "High"), color = line_colors[3], size=1.5, alpha=1) + 
  scale_linetype_manual(values = c(Low = "solid", Medium = "solid", High = "solid"),labels = c(Low = "Low", Medium = "Medium", High = "High")) +
  labs(color = "ID", linetype = "nV13AP") +
  guides(linetype = guide_legend(override.aes = list(color = line_colors)))

Plot_a.2

enter image description here

However, as you can observe, the colour assignment in the nV13AP legend is not correct, and I do not know why. Additionaly, the order of the nV13AP levels is not as I indicated in scale_linetype_manual. The order in the legend is High/Low/Medium while I would like to have either High/Medium/Low or Low/Medium/High.

Does anyone know where is the mistake? I checked that the colours assignment was wrong changing the values of the High line and observing which line changed in the plot, and I observed that was the dark red line which changed. So the light red colour for High in the legend is wrong!.

Upvotes: 0

Views: 123

Answers (1)

stefan
stefan

Reputation: 125038

The issue is that when using guide_legend you have to put pass color a vector of colors in the order they appear in the legend, i.e. the "High" color should come first, "Low" second, ... As you provided no data, I could not check but

guides(linetype = guide_legend(override.aes = list(color = line_colors[c(3, 1, 2)]))

should give you the right colors for your linetype legend.

Upvotes: 1

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