Plot main title in two lines

Question

I would like to have the title for the plot in two lines, but this does not work, why? and how can I make it work?

CVal<-1 
SumEpsVal<-2 
plot(1:10, main=bquote(paste("C=", .(CVal), " \n ", sum(xi), "=", .(SumEpsVal) )))

This here works:

plot(1:10, main=paste("C=1", "\n", "SumXi=2"))

I guess bquote makes something wrong... (look up ?bquote) I tried to change environment in bqoute (the where-argument) but I don't know which environment to take.

BTW:

plot(1:10, main=bquote(paste("C=", .(CVal), "bla \n ", sum(xi), "=", .(SumEpsVal) )))

makes something crazy with the "bla".

Answer 1

The root issue is that plotmath does not support newlines within the expressions to be output.

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

You really need to create and output each line separately.

For example :

Lines <- list(bquote(paste("C=", .(CVal))),
              bquote(paste(sum(xi), "=", .(SumEpsVal))))

Now output each line The text in the list is converted to expressions do.call

mtext(do.call(expression, Lines),side=3,line=0:1)