更改轴标签中多行之间的距离

Question

I need to plot two lines for x-axis label. Because I need to use special font I choose to use "expression" with "atop". The problem is that the distance between the two lines is much bigger than that if I just use "\\n". Like the following:

xlabs <- c('change in log2\nsample A', 
            expression(atop('change in'~log['2'], 'sample B')))

I got something like this:

Anyone knows how to solve the problem?

Answer 1

You can use the graphical parameter lheight together with mtext to adjust the line spacing to anything you want

plot(1:100, xlab = '')
par(lheight = 1.1)
mtext(xlabs[1], side = 1, line = 2)

Answer 2

I think using an expression vector is what was requested:

exl <- list(quote(line~1), quote(line~2))
plot(0:1,0:1,type="n",xlab="")
mtext(side=1, do.call(expression,exl),line=1:2)

These also succeeds (and might point the way to a more flexible approach to using an expression vector:

plot(0:1,0:1,type="n",xlab="")
mtext(side=1, expression(line*1, line*2), line=1:2)

plot(0:1,0:1,type="n",xlab="")
mtext(side=1, c(bquote(line==.(round(exp(1),2))), expression(line*2)), line=1:2)