Re: [R] Numerical question

2008-07-25 Thread Duncan Murdoch
On 25/07/2008 5:06 PM, Zhang Yanwei - Princeton-MRAm wrote: Hi all, I have n independent variables A_1, A_2, A_3,..,A_n, and each with known variances var(A_1), var(A_2),..., but unknown mean. How can I get the approximation of the variance of the product of the variables using numerical

Re: [R] Numerical question

2008-07-25 Thread Ted Harding
On 25-Jul-08 21:06:38, Zhang Yanwei - Princeton-MRAm wrote: > Hi all, >I have n independent variables A_1, A_2, A_3,..,A_n, and each > with known variances var(A_1), var(A_2),..., but unknown mean. How can > I get the approximation of the variance of the product of the variables > using num

Re: [R] Numerical question

2008-07-25 Thread stephen sefick
If it is in a data frame with the variables as columns try f <- cbind(a*b, b*c, c*d) sapply(f, function(x)var(x)) On Fri, Jul 25, 2008 at 5:06 PM, Zhang Yanwei - Princeton-MRAm < [EMAIL PROTECTED]> wrote: > Hi all, > I have n independent variables A_1, A_2, A_3,..,A_n, and each with > known

[R] Numerical question

2008-07-25 Thread Zhang Yanwei - Princeton-MRAm
Hi all, I have n independent variables A_1, A_2, A_3,..,A_n, and each with known variances var(A_1), var(A_2),..., but unknown mean. How can I get the approximation of the variance of the product of the variables using numerical computation, i.e. var(A_1*A_2*A_3*.*A_n)? Thanks. Since