ggplot geom_text annotation with variable label

Question

Is it possible to annotate a ggplot figure with a "text" element indicating a feature of the data (variable)?

library(ggplot2)
library(datasets)    
my.mean <- mean(mtcars$mpg, na.rm=T)
my.mean <- as.name(my.mean)

gplot <- ggplot(mtcars, aes(mpg))+geom_histogram()
gplot <- gplot + geom_text(aes_string(label=my.mean, y=5), size=3)

This produces something on the plot that looks like a succession of numbers. Any ideas how to resolve this?

Edit: this question is different since I am not trying to annotate each histogram bin with a value. The objective is to add one single text element to the plot.

Possible duplicate of How to get data labels for a histogram in ggplot2? — scoa
– scoa, Commented Oct 18, 2015 at 14:05
@ scoa: I can't see how the question you referred to is solving this one. Please suggest an explicit solution. — remi
– remi, Commented Oct 18, 2015 at 14:19

Matthias Munz · Accepted Answer · 2019-05-14 07:07:29Z

3

If I understood you right, you want to add a text to your plot which is defined by another dataset, i.e. a dataset which was not given as argument to ggplot().

Solution: Pass this dataset directly to your geom_text function using data=... to use it.

library(ggplot2) library(datasets)
my.mean <- mean(mtcars$mpg, na.rm=T)

ggplot(mtcars, aes(mpg)) +
        geom_histogram() + 
        geom_text(data=data.frame(my.mean=my.mean), aes(y=5, x=my.mean, label=my.mean), size=3)

edited May 14, 2019 at 7:07

answered Jul 21, 2018 at 16:10

Matthias Munz

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Comments

vanao veneri · Accepted Answer · 2015-10-18 15:20:25Z

2

it should work like this:

gplot <- gplot + geom_text(aes(15, 5, label="some random text"))
gplot

with the numbers you can specify the location within your grid.

answered Oct 18, 2015 at 15:20

vanao veneri

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2 Comments

remi Over a year ago

@ vano: I am trying to pass the value of my.mean to be printed on the plot instead of some text

vanao veneri Over a year ago

gplot <- gplot + geom_text(aes(15, 5, label=paste("Mean: ", my.mean)))

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