[R] VERY SIMPLE QUESTION

[Gavin Simpson]

On Fri, 2010-04-16 at 09:30 -0800, Kathie wrote:
> Dear R users,
> 
> I am looking for more efficient way to compute the followings
> 
> --------------------------------------------------------------------------
> 
> a <- matrix(c(1,1,1,1,2,2,2,2),4,2)
> b <- matrix(c(1,2,3,4),4,1)

Is there a reason why 'b' is a matrix?

Anyway, if b is a matrix with more cols in your real world problem,

sweep(a, 1, b[,1], "/")

will get what you want.

Otherwise

sweep(a, 1, b, "/")

will work whether b is a one col matrix or if you change it to a vector.

HTH

G

> 
> Eventually, I want to get this matrix, `c`.
> 
> c <- matrix(c(1/1,1/2,1/3,1/4,2/1,2/2,2/3,2/4),4,2)
> 
> --------------------------------------------------------------------------
> 
> In fact, #column of `a` is so big..
> 
> Is there a more efficient way to compute this instead of using "apply" or
> something? or "apply" is only way..?
> 
> Any suggestion will be greatly appreciated.
> 
> Regards,
> 
> Kathryn Lord 

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