On Nov 29, 2011, at 2:30 AM, Xu Wang wrote:
David,
Did my reply get orphaned
All replies are "orphaned". You are asked to include context if your
question relies on code that has previously been posted.
or are you trying to help me realize that asking
why something does not work is not a straightforward question? I'll
try to
cover both bases.
I'll focus just on the first case that I don't understand. Suppose
we have
s<- "ln(a+b)"
a<-1
b<-2
eval(parse(text=s))
Error in eval(expr, envir, enclos) : could not find function "ln"
Perhaps it's because I don't understand eval well (any good
references for
reading up on eval, parse, substitute, etc.?).
It appears you need to review the help page for the `log` function.
But I expected it to produce
the same as the following line:
eval(parse(text="ln(a+b)"))
It did.
> eval(parse(text="ln(a+b)"))
Error in eval(expr, envir, enclos) : could not find function "ln"
Xu
David Winsemius wrote
On Nov 29, 2011, at 2:00 AM, Xu Wang wrote:
Why don't the following two commands work?
eval(parse(text=s))
eval(as.expression(s))
They both "worked" as expected. An error was appropriately reported.
> ln(a+b)
Error: could not find function "ln"
> log(a+b)
[1] 1.098612
Can you think of anything else we might need to know in order to
answer that question?
Some Nabble users seem to expect that the rest of Rhelp sees what they
see. They are delusional when they do so.
--
David.
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David Winsemius, MD
West Hartford, CT
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