# [R] help on using sum in writng a function again

Gabor Grothendieck ggrothendieck at gmail.com
Mon Apr 10 05:23:36 CEST 2006

```Sorry, I replied to the wrong email.  Here it is again:

Try this where g is f summed over j and k for given scalars
theta and rho and gv is g vectorized over theta.  I have not
checked this carefully so be sure you do:

f <- function(theta = 0, rho = 0, j = 0, k = 0)
dnorm(theta+2*pi*j,0,1)*pnorm(2*pi*(k+1)-rho*(theta+2*pi*j))
g <- function(theta = 0, j = 0, k = 0)
sum(sapply(k, function(k) sum(f(theta, j = j, k = k))))
gv <- function(theta = 0, ...) sapply(theta, g, ...)

x <- seq(0, pi, length = 100)
plot(x, gv(x, j = -1:1, k = -1:1))

On 4/9/06, skim033 at student.ucr.edu <skim033 at student.ucr.edu> wrote:
> Here I would like to ask you again more directly.
> The following is what I had for now.
> The function to begin with is
> dnorm(theta+2*pi*j,0,1)*(pnorm(((2*pi*(k+1)-rho*
> (theta+2*pi*j)).
>
> Now, I wanted to sum it over k from -10000 to 10000. So, I
> wrote the following.
> f1<-function(theta,j){
> aa<-seq(-10000,10000,lenght=20001)
> sum(dnorm(theta+2*pi*j,0,1)*(pnorm(((2*pi*(aa+1)-rho*
> (theta+2*pi*j))
> }
>
> Next, I would like sum over j as
> (This is a way I thouhgt about computing a double sum)
> f2<-function(theta){
> aa<-c(-1,0,1)
> sum(f(theta,aa))
> }
> expecting f2 be a function of theta.
>
> Then, I wanted to plot f2 for theta from 0 to 2*pi. But, f2
> (seq(0,2*pi,length=10)) is a scalar, not a vector with the
> dimension of 10x1. I would like to ask you how I can use
> rowSums with outer or some other method to correct my coding.
>
> I would like to thank you in advance.
> Sungsu.
> UC riverside.
>
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