How to annotate a ggplot2 plot with latex2exp using variables?

Question

Here is my sample code.

library(ggplot2)
library(latex2exp)
p1 <- ggplot(mtcars, aes(x = wt, y = mpg)) + geom_point()
alpha=10
beta=20
p1 + annotate("label", x = 4, y = 25, label = TeX("$y = alpha e ^{betax}$"))

I was trying to get a label like y=10e^{20x}. Is it possible with latex2exp or is there better way?

Thanks

mrhd · Accepted Answer · 2020-04-23 07:20:31Z

2

One way to do it with latex2exp would be to use sprintf to construct the LaTeX string:

p1 + annotate("label", x = 4, y = 25, label = TeX(sprintf("$y = %d e ^{%dx}$", alpha, beta)))

answered Apr 23, 2020 at 7:20

mrhd

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Comments

Matthew Hui · Accepted Answer · 2020-04-23 07:12:47Z

1

Try TeX(paste("$y = ", alpha, "e ^{", beta, " x}$"))?

answered Apr 23, 2020 at 7:12

Matthew Hui

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1 Comment

murpholinox Over a year ago

Works but I get a warning: is.na() applied to non-(list or vector) of type 'expression'

yang · Accepted Answer · 2020-04-23 08:02:45Z

1

You can use bquote() or paste() , and set the argument parse=TRUE

library(ggplot2)
p1 <- ggplot(mtcars, aes(x = wt, y = mpg)) + geom_point()
alpha=10
beta=20
p1 + 
  annotate("label", 
           x = 4, y = 25, 
           label = list(bquote(y==.(alpha)*e^{.(beta)*x})), parse= TRUE
  )


p1 + 
  annotate("label", 
           x = 4, y = 25, 
           label = paste("y==", alpha, "*e^", "{", beta, "*x}"), parse= TRUE
  )

^{Created on 2020-04-23 by the reprex package (v0.3.0)}

Hopes helpful for you.

answered Apr 23, 2020 at 8:02

yang

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2 Comments

Matthew Hui Over a year ago

A while ago I tried label = bquote(y==.(alpha)*e^{.(beta)*x}). The result is perfect except that a redundant pair of brackets appears after the equation. Do you have any idea why?

yang Over a year ago

@MatthewHui Sorry, I have no idea why. And it requires coerce your label to a list, such as list(bquote(y==.(alpha)*e^{.(beta)*x}))

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