[R] embedding expression into title in R plot

[Evan Cooch]

Suppose I've specified that the xlab for a plot is

expression(bold(species~(italic(N1))))

In other words, I want the axis label to be bold, italic 'species (N1)'

Now, I want the title for the plot to be have this label embedded in the 
title.

Say, 'This is the plot for Species (N1)'.

For a variety of reasons, I've set this up so that the xlab is a global 
parameter (basically, because the labels are set in a function which 
when called, generates various plots):

x_label <<- expression(bold(species~(italic(N1))))

So, in the title, I've tried

  title(main=paste("This is the plot for ",x_label,"nullcline", sep=" "));

but what this does is generate something like

'This is the plot for bold(species~(italic(N1)))'

In other words, it pastes the text of the expression into the title, but 
not what the expression 'evaluates' to.

Is there any way around this?

Thanks in advance...


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