New line in caption with math symbols embedded in expression (paste(

Note, from ?plotmath:

"Control characters (e.g., \n) are not interpreted in character strings in
plotmath, unlike normal plotting."

For this reason, as best I can tell, you need to fool with plotmath's
"atop" command or do separate "labs" calls.  This post seems to confirm
that opinion:


https://stackoverflow.com/questions/29112697/adding-a-newline-in-a-substitute-expression

I certainly would welcome a better alternative.

Cheers,
Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Thu, Feb 18, 2021 at 9:37 AM Izmirlian, Grant (NIH/NCI) [E] via R-help <
r-help at r-project.org> wrote:

## I am using ggplot and trying to produce a caption containing math
symbols. I need to
## add a second line. I did a fair amount of googling for answers. This
one seemed like
## it would answer my question as it is nearly exactly my problem, except
there is only
## one argument to the paste function. Note that my example is a complete
minimal
## example, just a scatterplot with a line, and the caption content seems
to not have
## anything to do with the plot. That is of course, intentional.
##
##
https://stackoverflow.com/questions/13223846/ggplot2-two-line-label-with-expression

library(ggplot2)
X <- 10*runif(100)
Y <- 2*X + rnorm(100, sd=2)
fit <- lm(Y~X)
Y.p <- predict(fit, newdata=data.frame(X=X))
DAT <- data.frame(X=X)

## without a newline
p <- ggplot(data=DAT, aes(x=X)) + geom_point(aes(y=Y)) +
geom_line(aes(y=Y.p))
p <- p + labs(caption=expression(paste(P,"(",FDP,">", alpha,") ",
                        "for 'FDR' and 'Auto' FDP control method, vs '",
m,
                        "' at levels of 'eff size' (col) and '", p[1], "'
(row)")))
p <- p + theme(plot.caption = element_text(hjust = 0))

## newline, method 1, just add a new component of paste containing "\n"
somewhere in the middle
p <- ggplot(data=DAT, aes(x=X)) + geom_point(aes(y=Y)) +
geom_line(aes(y=Y.p))
p <- p + labs(caption=expression(paste(P,"(",FDP,">", alpha,") ",
                        "for 'FDR' and 'Auto' FDP control method, vs '",
m,
                        "' at levels of 'eff size' (col) and '", p[1], "'
(row)",
                        "and \n a new line")))
p <- p + theme(plot.caption = element_text(hjust = 0))

## doesn't work because the newline affects only the last component of
paste. It looks like new line
## works if the line is long enough, but the newline character is being
parsed until the individual
## arguments to paste are parsed for math symbols but prior to pasting
the components together. prior
## to pasting all arguments. I can't imagine why this would be the
desired behavior. When the value of a
## caption argument is expression(paste(s1, s2, s3, ...)) then parsing
for a newline character should
## occur after the components are pasted together, right?

## newline, method 2, enclose paste in another paste and add the new line
as the second argument of the
## outer paste
p <- ggplot(data=DAT, aes(x=X)) + geom_point(aes(y=Y)) +
geom_line(aes(y=Y.p))
p <- p + labs(caption=expression(paste(paste(P,"(",FDP,">", alpha,") ",
                        "for 'FDR' and 'Auto' FDP control method, vs '",
m,
                        "' at levels of 'eff size' (col) and '", p[1], "'
(row)"),
                        "and \n a new line")))
p <- p + theme(plot.caption = element_text(hjust = 0))

## which has the same behavior


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