I am trying to label a plot with the following label:
"Some Assay EC50 (uM)" where the "u" is a micro symbol.
I currently have:
assay <- "Some Assay"
plot(0,xlab=expression(paste(assay," AC50 (",mu,"M)",sep="")))
But that gives: "assay EC50 (uM)" rather than the desired "Some Assay EC50 (uM)".
Suggestions? Thanks.
I also tried:
paste(assay,expression(paste(" AC50 (",mu,"M)",sep="")),sep="")
You want a combination of bquote() and a bit of plotmath fu:
assay <- "Some Assay"
xlab <- bquote(.(assay) ~ AC50 ~ (mu*M))
plot(0, xlab = xlab)
The ~ is a spacing operator and * means juxtapose the contents to the left and right of the operator. In bquote(), anything wrapped in .( ) will be looked up and replaced with the value of the named object; so .(assay) will be replaced in the expression with Some Assay.
Using tidy_eval approach you could do
library(rlang)
assay <- "Some Assay"
plot(0,xlab=expr(paste(!!assay," AC50 (",mu,"M)",sep="")))
expr and !! are included in tidyverse, so you don't actually need to load rlang. I just put it there to be explicit about where they come from.
another option using mtext and bquote
plot(0,xlab='')
Lines <- list(bquote(paste(assay," AC50 (",mu,"M)",sep="")))
mtext(do.call(expression, Lines),side=1,line=3)
Note that I set the xlab to null in the first plot.
EDIT No need to call expression, since bquote will create an expression with replacement of elements wrapped in .( ) by their value. So a goodanswer is :
plot(0,xlab='')
Lines <- bquote(paste(.(assay)," AC50 (",mu,"M)",sep=""))
mtext(Lines,side=1,line=3)
bquote() which is to form an expression with replacement of elements wrapped in .( ) by their value.
do.call(expression, Lines) to make expression expanded, using the after-edit suggestion wrote literally the expression.You also could try the poor man's approach:
assay <- "Some Assay"
plot(0, xlab = paste0(assay, " AC50 (µM)"))
It specifies the mu character directly rather than using expressions (and paste0 is just paste with sep = "").
Replacing expression() with eval() + parse() works when including a string variable.
Note that all spaces have to be replaced by ~, hence the call to gsub on the assay variable below. I've replaced the spaces in place in the rest of the label (e.g. " AC50 (mu*M)" --> "~AC50~(mu*M)")
assay <- "Some Assay"
plot(0,xlab=eval(parse(text = paste0(gsub(' ', '~', assay),"~AC50~(mu*M)"))))
