[R] How to customize legend labels in ggplot2?

[Luigi Marongiu]

Thank you, but then I will have long labels also on the axis, making the
plot too crowded. I would like instead to force the long labels only on the
legend...

On Wed, 12 Mar 2025, 12:47 Rui Barradas, <ruipbarradas using sapo.pt> wrote:

> Às 10:35 de 12/03/2025, Luigi Marongiu escreveu:
> > I have a data frame with measurements in different conditions. I set
> > the conditions as a factor using a notation for ease of use. I now
> > want to plot the data and assign meaningful labels to the factors. I
> > am using ggplot2; for the x axis I would like to keep the factors but
> > in the legend I would like to use custom values.
> > I tried different combinations but none worked.
> > What is the correct way to assign
> > custom labels to legends in ggplot2?
> > Thank you
> >
> > EXAMPLE:
> > ```
> > df = data.frame(Target = 1:4,
> >                  Rate = c(0.02078663, 0.03685543, 0.02238002,
> 0.05033979),
> >                  SD = c(0.003043398, 0.001447410, 0.002998729,
> 0.002171813))
> > df$Target = factor(df$Target)
> > ggplot(df, aes(x=Target, y=Rate, colour=Target, group=Target)) +
> >    geom_point(size=8) +
> >    geom_errorbar(aes(ymin=Rate-SD, ymax=Rate+SD), width=.1) +
> >    scale_colour_manual(values = COLS) +
> >    xlab(expression(bold("Class"))) +
> >    ylab(expression(bold("Value"))) +
> >    theme_classic(base_size = 15)
> > ```
> > NOTE: if using
> > ```
> > ...
> >    theme_classic(base_size = 15, labels = c("Condition 1", "Condition 2",
> >                                             "Condition 3", "Control"))
> > ```
> > I get the error:
> >
> > Error in theme_classic(base_size = 15, labels = c("Condition 1",
> > "Condition 2",  :
> >    unused argument (labels = c("Condition 1", "Condition 2", "Condition
> > 3", "Control"))
> >
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> > and provide commented, minimal, self-contained, reproducible code.
> Hello,
>
> The colors COLS are missing from the question.
> As for the labels, use
>
>
> lbls <- c("Condition 1", "Condition 2", "Condition 3", "Control")
>
> and then
>
> scale_colour_manual(values = COLS, labels = lbls)
>
>
> Hope this helps,
>
> Rui Barradas
>
>
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