On 11/29/2011 06:30 PM, Xu Wang wrote:
David,
Did my reply get orphaned 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.?). But I expected it to produce
the same as the following line:
eval(parse(text="ln(a+b)"))
Hi Xu,
Try:
s<-"log(a+b)"
a<-1
b<-2
eval(parse(text=s))
[1] 1.098612
There is no "ln" function in the base package.
Jim
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