问题
When run the following code, I obtain Error in as.graphicsAnnot(text) : could not find function "bold"
. How can I fix this?
my.qq <- function(x, main=expression(bold(italic(F)~~"Q-Q plot")),
margs=list(side=3, cex=par("cex.main"), font=par("font.main"),
adj=par("adj"), xpd=NA), ...)
{
plot(qnorm(ppoints(n <- length(x))), sort(x), ...)
do.call(mtext, c(list(main), margs))
}
x <- rnorm(100)
my.qq(x)
my.qq(x, main=substitute(bold(italic(F)[N(mu.,s2.)]~~"Q-Q plot"), list(mu.=0, s2.=1))) # fails
My goal is to use the list margs
to pass additional arguments to mtext()
. That's normally done with ...
, but those arguments are already passed to plot()
.
回答1:
substitute
in this case returns an language object, not an expression. the expression expression
is used loosely in R
, however here it appears that mtext
needs an object of class expression
.
You can ensure this by wrapping substitute(...)
in as.expression()
my.qq(x, main=as.expression(substitute(bold(italic(F)[N(mu.,s2.)]~~"Q-Q plot"), list(mu.=0, s2.=1))))
or more simply by passing an expression to substitute (as would be required in a normal call to mtext
)
my.qq(x, main=substitute(expression(bold(italic(F)[N(mu.,s2.)]~~"Q-Q plot")), list(mu.=0, s2.=1)))
Both the examples above will produce
There is a note in the help for substitute
Substituting and quoting often cause confusion when the argument is expression(...). The result is a call to the expression constructor function and needs to be evaluated with eval to give the actual expression object.
however in this case eval
is not required
来源:https://stackoverflow.com/questions/13982856/plot-and-do-call-how-to-pass-expressions-to-plot-title-when-is-used-o