linebreak and superscript in bquote axis label ggplot2

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.