Data visualization in R, particularly with the powerful ggplot2 package, allows for the creation of intricate and informative plots. However, sometimes minor visual quirks can arise, demanding specific solutions. One common challenge that users encounter is how to remove ‘a’ from legend when using aesthetics and geom_text. This seemingly small ‘a’ often appears as an unwanted legend entry, cluttering your otherwise pristine data visualizations. It typically emerges when geom_text() or geom_label() is used with an aesthetic mapping, even if that mapping isn’t directly intended to create a legend. Understanding why this happens and, more importantly, how to effectively address it is crucial for generating publication-ready graphics.
Understanding the ‘a’ Legend Entry in ggplot2
The appearance of an ‘a’ in your ggplot2 legend when using geom_text() or geom_label() is a consequence of how ggplot2 handles aesthetic mappings. By default, if you map any variable to an aesthetic within a geom function, ggplot2 assumes you might want that mapping to be represented in the legend. For instance, if you write geom_text(aes(label = my_variable)), ggplot2 interprets the label aesthetic as a potential candidate for a legend entry, even though text labels themselves don’t typically require a legend key.
This behavior is less about an error and more about ggplot2’s comprehensive approach to ensuring all mapped aesthetics are accounted for. The ‘a’ specifically refers to the default text aesthetic. When you include geom_text() with an aesthetic like label inside aes(), ggplot2 internally tries to create a legend for this aesthetic. Since text itself doesn’t have a color, shape, or size that typically gets mapped to a legend, it defaults to a generic representation, often appearing as an ‘a’ or a blank box, which can be quite confusing for viewers.
While a quick fix might seem to be setting show.legend = FALSE within the geom_text() layer, this often proves too broad. It hides any legitimate legend entries that might arise from other aesthetic mappings within that specific geom, which might not be your intention. Instead, a more precise method is required to specifically target and remove ‘a’ from legend when using aesthetics and geom_text without affecting other vital legend components.
The Primary Solution: Suppressing Specific Legend Keys with guides()
The most robust and recommended way to manage unwanted legend entries, including the elusive ‘a’ from geom_text, is by leveraging the guides() function in ggplot2. This function provides granular control over the appearance and presence of individual legends. Specifically, you can tell ggplot2 to suppress the legend for a particular aesthetic by setting its guide to "none".
For example, if the ‘a’ legend entry is appearing due to an implicit mapping of the label aesthetic within geom_text(), you can instruct ggplot2 to ignore any legend associated with the ’label’ aesthetic. The syntax for this is straightforward: guides(color = "none", fill = "none", size = "none", etc.). While geom_text doesn’t directly map to ‘color’ or ‘fill’ in the same way other geoms do, the ‘a’ frequently appears as a result of a default internal mapping that ggplot2 tries to create for the ’text’ aesthetic. Therefore, targeting the ‘color’ or ‘fill’ guide, even if not explicitly defined in aes() for geom_text, often resolves the issue. This is because text labels, by default, often inherit the color aesthetic of the underlying layer.
Consider this example code snippet:
library(ggplot2) data <- data.frame( x = 1:5, y = c(2, 4, 1, 5, 3), label_text = LETTERS[1:5], group = c("A", "B", "A", "B", "A") ) Plot causing the 'a' legend entry p <- ggplot(data, aes(x = x, y = y)) + geom_point(aes(color = group), size = 4) + geom_text(aes(label = label_text), nudge_y = 0.5) To remove 'a' from legend when using aesthetics and geom_text p_fixed <- p + guides(color = guide_legend(), label = "none") 'label' guide might appear for geom_label p_fixed Renders plot without the unwanted 'a' legend
In many cases, simply using guides(color = "none") or guides(fill = "none") will be sufficient, as the ‘a’ often manifests under these default aesthetic keys. This method offers surgical precision, ensuring you only hide the specific legend you intend to. According to the official ggplot2 documentation on guides, this function is the definitive way to control legend appearance.
Alternative: Managing Aesthetics with scale_colour_manual() or scale_fill_manual()
While guides() is the primary method to remove ‘a’ from legend when using aesthetics and geom_text, another powerful approach involves explicit control over your scales, specifically scale_colour_manual() or scale_fill_manual(). This method is particularly useful when you have other aesthetic mappings (like color for points or lines) that you do want to retain in the legend, but the geom_text layer is causing an additional, unwanted entry.
When you use scale_colour_manual() or similar scale functions, you gain fine-grained control over how colors are mapped to data values and, crucially, how their corresponding legends are displayed. By setting guide = "none" directly within the scale function that is implicitly or explicitly linked to the ‘a’ legend entry, you can suppress it. This is often effective when geom_text inherits a Question & Answer :
How can I can remove the letter ‘a’ from the legend generated by this code? If I remove the geom_text, then the ‘a’ letter will not show in the legend. I want to keep geom_text, though.
ggplot(data = iris, aes(x = Sepal.Length, y=Sepal.Width, shape = Species, colour = Species)) + geom_point() + geom_text(aes(label = Species))
Set show.legend = FALSE in geom_text:
ggplot(data = iris, aes(x = Sepal.Length, y = Sepal.Width, colour = Species, shape = Species, label = Species)) + geom_point() + geom_text(show.legend = FALSE)
The argument show_guide changed name to show.legend in ggplot2 2.0.0 (see release news).
Pre-ggplot2 2.0.0:
With show_guide = FALSE like so…
ggplot(data = iris, aes(x = Sepal.Length, y = Sepal.Width , colour = Species, shape = Species, label = Species ), size = 20) + geom_point() + geom_text(show_guide = FALSE)
