linebreak and superscript in bquote axis label ggplot2 - r

Question

After looking at many examples and lots of trying, I'm still failing to combine text strings and an expression into ggplot2 axis labels to exactly what I want.
what I am trying to get here is the x-axis label to be:
the ingredients:
parname <- 'FL.Red.Total'
xmean <- 123.34
xsigma <- 2580.23
to change the numbers to 10^n notations I use this formula:
sci_form10 <- function(x) {
paste(gsub("e\\+", " \xB7 10^", scientific_format()(x)))
}
the name would then be build by:
labs( x = bquote(.(gsub('\\.', '\\ ', parname)) ~ " (a.u.) (" ~ mu ~ "=" ~ .(sci_form10(xmean)) ~ ", " ~ sigma ~ " =" ~ .(sci_form10(xsigma)) ~ ")" ))
I'm hoping to replace 10^04 with 10 followed by a 4 in superscript and to add a linebreak to the labels as the first image shows
The test code:
library(ggplot2)
library(scales)
sci_form10 <- function(x) {
paste(gsub("e\\+", " * 10^", scientific_format()(x)))
}
parname <- 'FL.Red.Total'
xmean <- 123.34
xsigma <- 2580.23
ggplot(mtcars, aes(x=mpg,y=cyl)) +
geom_point() +
labs( x = bquote(.(gsub('\\.', '\\ ', parname)) ~ " (a.u.) (" ~ mu ~ "=" ~ .(sci_form10(xmean)) ~ ", " ~ sigma ~ " =" ~ .(sci_form10(xsigma)) ~ ")" ))
gives:
p.s. I also tried
sci_form10 <- function(x) {
paste(gsub(".*e\\+", "10^", scientific_format()(x)))
}
which only gives the 10^03 part to see if that would change the outcome of my label, but no.

Answer 1

An option would be wrap with atop to create line breaks
sci_form10 <- function(x) {
paste(gsub("e\\+", " \u00B7 10^", scientific_format()(x)))
}
x1 <- sci_form10(xmean)
x2 <- sci_form10(xsigma)
lst1 <- strsplit(c(x1,x2), "\\s(?=10)", perl = TRUE)
pre <- sapply(lst1, `[`, 1)
post <- sapply(lst1, `[`, 2)
xmean1 <- parse(text = paste0("'", pre[1], "'"))[[1]]
xsigma1 <- parse(text = paste0("'", pre[2], "'"))[[1]]
post1 <- parse(text = post[1])[[1]]
post2 <- parse(text = post[2])[[1]]
ggplot(mtcars, aes(x=mpg,y=cyl)) +
geom_point() +
labs( x = bquote(atop(.(gsub("\\.", "\\ ",
parname))~"(a.u.)"~phantom(), "(" ~ mu~ " = "~ .(xmean1) ~ .(post1) ~ ", " ~ sigma ~ " = " ~ .(xsigma1) ~ .(post2)~ ")")))
-output

Answer 2

I have something that does most of what you wanted.
changeSciNot <- function(n) {
output <- format(n, digits=3, scientific = TRUE) # Transforms the number into scientific notation even if small
output <- sub("e", "*10^", output) # Replace e with 10^
output <- sub("\\+0?", "", output) # Remove + symbol and leading zeros on exponent, if > 1
output <- sub("-0?", "-", output) # Leaves - symbol but removes leading zeros on exponent, if < 1
output
}
# example data
parname <- "FL.Red.Total"
xmean <- 123.34
xsigma <- 2580.23
label <- bquote(atop(.(gsub("\\.", "\\ ", parname)) ~ "(a.u.)",
mu*"="*.(changeSciNot(xmean))*"," ~ sigma*"="*.(changeSciNot(xsigma))))
ggplot(mtcars, aes(x=mpg,y=cyl)) +
geom_point() +
labs(x = label)
The changeSciNot function came from this thread. I had some problems using \xB7 for the multiplication, so I left *. I also hard coded the number of digits for the format, but you can also make it into an argument. Hopefully, this will get you closer to the exact desired output.