On May 2, 2009, at 12:18 AM, RON70 wrote:
Can anyone please explain me why it is not coming? I have done
following :
j=1
i=0:j; sum( choose(i+j,i) )
[1] 3
j=2
i=0:j; sum( choose(i+j,i) )
[1] 10
j=3
i=0:j; sum( choose(i+j,i) )
[1] 35
j=0:3; i=0:j; sum( choose(i+j,i) )
Warning message:
In 0:j : numerical expression has 4 elements: only the first used
[1] 4
Here if value of "j" is given independently it is ok. However as
soon as "j"
is used in loop it fails?
What loop? You made j a vector and then tried to treat it like a
single value. You even got an informative error message:
"Warning message:
In 0:j : numerical expression has 4 elements: only the first used"
Why it is happening? Is there any mathematics behind that?
Read for meaning.
Orestis Chrysafis wrote:
Dear R experts
I need to write a function that incorporates double summation, the
problem
being that the upper limit of the second summation is the index of
the
first
summation, i.e:
sum_{j=0}^{x} sum_{i=0}^{j} choose(i+j, i)
where x variable or constant, doesn't matter.
The following code obviously doesn't work:
f=function(x) {j=0:x; i=0:j; sum( choose(i+j,i) ) }
Can you help?
Thanks in advance,
Orestis Chrysafis
School of Mathematics
University of Sheffield
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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