On 04/05/2010 5:05 PM, Ruihong Huang wrote:
Hi All,
I have two questions on R. Could you please explain them to me? Thank you!
1) When call a function, R typically copys the values to formal
arguments (call by value). This is very cost, if I would like to pass a
huge data set to a function. Is there any situations that R doesn't copy
the data, besides pass data in an environment object.
R doesn't copy data unless it needs to, for example if your function
modifies its copy. So don't worry about the cost, there usually isn't
much of one.
2) Does R pre-compile the object function to binary when running
"optim"? I experienced the R "optim" is much slower than the MATLAB
"fmincon" function. I don't know MATLAB has done any pre-compilation on
the script for object function or not. But perhaps, we can increase R
performance by some sort of pre-compilation during running time.
There's an experimental compiler, but I don't know if there's a
predicted release date for it. R is not an easy language to compile.
Duncan Murdoch
Thanks in advance.
Best Regards,
Ruihong
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