Dynamic subscript for text with an R expression

Question

I want to generate dynamically a subscript for a text in a plot with an R expression. The text of the three points in the plot below should be $\pi_1$ , $\pi_2$ , and $\pi_3$ .

lbs <- vector()
for(i in 1:3) lbs <- append(lbs, expression(pi[i]))

plot(1:3)
text(1:3, labels=lbs)

The Greek letter appears, but the subscript remains as i. I've tried bquote as well but without success.

I appreciate any suggestions.

This isn't working? stackoverflow.com/questions/4302367/… Or this? stackoverflow.com/questions/20532136/… — Roman Luštrik
– Roman Luštrik, Commented Nov 23, 2017 at 10:05
Thanks, but these examples are for a single stamp in the plot (main tile xlab, ylab, etc.) I have not seen one for text in the plot. — JARO
– JARO, Commented Nov 23, 2017 at 10:09

Alex · Accepted Answer · 2017-11-23 10:18:58Z

2

Try this

lbs <- vector()
for(i in 1:3) lbs <- append(lbs, parse(text=(paste0("pi[",i,"]"))))

plot(1:3)
text(1:3, labels=lbs)

I am sure that there are better solutions but this is working. The problem with your code is that everything inside expression() is not evaluated. parse() evaluates and then returns an expression.

edited Nov 23, 2017 at 10:18

answered Nov 23, 2017 at 10:13

Alex

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