2) The plotmath Help state that expressions can be used for axis labels, so I would have expected the above to work without the eval()call -- but it does not. Would someone kindly explain to me why not -- i.e., what I have misunderstood. That is, to be clear, why does the following not work:
Because substitute() doesn't evaluate its argument: the result is not an expression but a call to the expression() function.
An example where it is clearer what is going on
substitute(log(x),list(x=1))
doesn't return a number, even though log() returns a number. It returns a call to log() that still has to be evaluated
-thomas
for(i in seq(-3,to=3)) axis(1,at=i, lab=switch(sign(i)+2, substitute(expression(mu-j*sigma),list(j=i)), expression(mu), substitute(expression(mu+j*sigma),list(j=i))))
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