Error when using expression as label in ggplot

Question

I tried searching, but this bothers me quite a bit, as it in my opinion should be a simple line of coding. However, i keep getting an error when trying...

Firstly, this code works fine

  scale_linetype_manual("",
                    values=c("pAl"=4,"pAlOH"=3, "pAl7OH17"=6, "pAl13OH34"=2,"pAlOH4"=1,"pAl2OH2"=5),
                    labels = c(expression("Al"^"3+"),
                               expression("Al(OH)"^"2+"),
                               expression("Al7(OH)"[17]^"4+"),
                               expression("Al13(OH)"[34]^"5+"),
                               expression("Al(OH)"[4]^"-"),
                               expression("Al2(OH)"[2]^"4+")))+

I do, however, want some of the numbers after Al to be subscripted too, but when trying

  expression("Al"[2]"(OH)"^"2+") or expression("Al" ~ [2] ~ "(OH)" ~ ^ ~ "2+")

or whatever variant i can come up with, i keep getting an error.

Again, there's probably an easy fix. Sorry for my lack of experience in using R :)

Maybe i should have added that this is an extension to my ggplot code. I plot concentrations against pH and want a legend explaining the different linetypes. — Chemistry101
– Chemistry101, Commented Nov 23, 2017 at 0:41

baptiste · Accepted Answer · 2017-11-23 01:04:59Z

1

library(grid)

e <- c("Al[2]~(OH)^'2+'", 
       "Al[7]~(OH)[17]^'4+'")
grid.newpage()
grid.text(parse(text=e), y=c(0.4,0.6))

answered Nov 23, 2017 at 1:04

baptiste

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3 Comments

Chemistry101 Over a year ago

Thanks, but when is this converted to an expression instead of just pure text? Inside the grid function? I might be dumb right now, but i can't really figure out how to integrate this into my code. Maybe my full code is required to understand it? Using "Al[7]~(OH)[17]^'4+'" in my string just makes nothing subscripted but instead everything is plain text.

Chemistry101 Over a year ago

I still didn't solve this issue, do you have any ideas?

baptiste Over a year ago

@Chemistry101 you have not provided a reproducible example

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