user3633161 user3633161 - 15 days ago 7
R Question

Editing legend (text) labels in ggplot

I have spent hours looking in the documentation and on StackOverflow, but no solution seems to solve my problem. When using

ggplot
I cann't get the right text in the legend, even though it's in my dataframe. I have tried
scale_colour_manual
,
scale_fill_manual
with different values for
labels=
such as
c("T999", "T888")", "cols"
.

Here is my code:

T999 <- runif(10, 100, 200)
T888 <- runif(10, 200, 300)
TY <- runif(10, 20, 30)
df <- data.frame(T999, T888, TY)


ggplot(data = df, aes(x=T999, y=TY, pointtype="T999")) +
geom_point(size = 15, colour = "darkblue") +
geom_point(data = df, aes(x=T888, y=TY), colour = 'red', size = 10 ) +
theme(axis.text.x = element_text(size = 20), axis.title.x =element_text(size = 20), axis.text.y = element_text(size = 20)) +
xlab("Txxx") + ylab("TY [°C]") + labs(title="temperatures", size = 15) +
scale_colour_manual(labels = c("T999", "T888"), values = c("darkblue", "red")) + theme(legend.position="topright")


Help would be very appreciated! Thx.

Answer

The tutorial @Henrik mentioned is an excellent resource for learning how to create plots with the ggplot2 package.

An example with your data:

# transforming the data from wide to long
library(reshape2)
dfm <- melt(df, id="TY")

# creating a scatterplot
ggplot(data = dfm, aes(x=TY, y=value, color=variable)) + 
  geom_point(size=5) +
  labs(title = "Temperatures\n", x = "TY [°C]", y = "Txxx", color = "Legend Title\n") +
  scale_color_manual(labels = c("T999", "T888"), values = c("blue", "red")) +
  theme_bw() +
  theme(axis.text.x=element_text(size=14), axis.title.x=element_text(size=16),
        axis.text.y=element_text(size=14), axis.title.x=element_text(size=16),
        plot.title=element_text(size=20, face="bold", color="darkgreen"))

this results in:

enter image description here

As mentioned by @user2739472 in the comments: If you only want to change the legend text labels and not the colours from ggplot's default palette, you can use scale_color_hue(labels = c("T999", "T888")) instead of scale_color_manual().