Evaluate an Argument If Possible
This function parses, evaluates and returns the string given as its
first argument. If it can't, the argument itself is returned. Use of
evalOrEcho to process arguments inside a function can make for
more flexible code.
a string or other object to attempt to parse and evaluate.
a string or NULL. If non-NULL, the evaluation of
parent generations to go back. The evaluation is attempted in the
enviroment specified by
Using this function inside another function to process some of its
arguments can be very useful. For example,
tisPlot has a
number or arguments that specify text labels for headers, subheaders,
footnotes, axis labels, and so on. One of those arguments is
sub, which specifies the subheader. By doing this:
sub <- evalOrEcho(sub, resultMode = "character")
tisPlot can handle the
sub argument given in any of
sub = "This is a simple subtitle".
sub = c("this is a two", "line subtitle").
sub = 'c("this is another", "two line subtitle")'.
x is successfully parsed and evaluated, and its mode matches
resultMode (if supplied), the resulting object is returned.
x itself is returned.
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