[R] summation sign

[peter dalgaard]

On Oct 27, 2012, at 01:34 , sffarooqi wrote:

> 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