Using a string variable in expression for R for subscript/superscript

Question

We can use subscript or superscript in a plot title in R using the following

plot(1,1, main=expression('title'^2))  #superscript

plot(1,1, main=expression('title'[2])) #subscript

However, what if I want to use a string variable in expression. For example,

my_string="'title'^2"

plot(1,1, main=expression(my_string))

Clearly, this doesn't work and the plot title just becomes my_string rather than title^2.

Is it possible to use a string variable inside expression?

Thanks, Brij.

MrFlick · Accepted Answer · 2018-06-13 16:46:06Z

0

In order to make an expression from a string, you need to parse it. Try this

my_string <- "'title'^2"
my_title <- parse(text=my_string)
plot(1,1, main=my_title)

If you just wanted to swap out certain parts of the expression with a string value, you can use something like bquote

my_string <- "title"
my_title <- bquote(.(my_string)^2)
plot(1,1, main=my_title)

answered Jun 13, 2018 at 16:46

MrFlick

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4 Comments

Brij Mohan Over a year ago

Thank you. This seems to work. But it appears if I use my_string <- "'my title'^2", then the space between my and title confuses parse.

MrFlick Over a year ago

I cannot reproduce that problem. parse(text=my_string) with the my_string you provided works just fine for me. Are you sure your inner string is in quotes?

Brij Mohan Over a year ago

I had an additional step in my code and I figured it out. Thank you for your time and help. Much appreciated.

Alvaro Morales Over a year ago

How to get 2 as some variable?

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