summation sign

Hi all,
I have a very quick question on how to use the summation sign in R for the
function.
Here?s a basic example: the function is sum(i=1 to 5)log(1-xi^2)
Id be grateful if someone knows how to do this without writing it out 5
times - I am looking sth along the lines of  the following:

computeR <- function(x)
 {
   return (-sum(log(1-x^2))
}^
thank you vm in advance!

You pretty much did it already:

x <- c(.5,.6,.7,.4,.8)
-sum(log(1-x^2))

[1] 2.603318

I.e., just have x as a vector of length 5 and the rest is done automagically.

(And, BTW, you don't need return() in a function like that in R, the return value is the value of the last expression.)

Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com

thank you vm for the reply! Just to make things a little more complicated
--does the equation hold even if the values of x are unknown? More
specifically perhaps we can still refer to the made up example 
Sum(n equal 5)log(1-xi^2) 

In the problem I am working on, I am writing a modified Newton Optimisation
code with linesearch. Therefore the values of x are not given but each x
variable is some nx1 vector ..e.g. lets take a 3x1 vector. 
So referring to this example, where we had to sum 5 times, how could I write
the function such that it sums 5 times, but each of the 5 x variables is
taken to be a 3x1 vector.  

thank you very much again!




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