On 30-12-2012, at 11:26, meng <laomen...@163.com> wrote:
> hi all:
> Here's a dataframe(dat) and a vector(z):
>
> dat:
> x1 x2 x3
> 0.2 1.2 2.5
> 0.5 2 5
> 0.8 3 6.2
>
>> z
> [1] 10 100 100
>
> I wanna do the following:
> 10*x1,100*x2,1000*x3
>
> My solution is using the loop for z and dat(since the length of z is the same
> as ncol of dat),which is tedious.
> I wanna an efficient solution to do it .
Data:
xdat <- data.frame(x1=c(.2,.5,.8),x2=c(1.2,2,3),x3=c(2.5,5,6.2))
z <- c(10,100,1000)
Assuming you want a dataframe as result you can do one of the following
Option 1:
------------
as.data.frame(sapply(1:length(z),function(k)xdat[k]*z[k]))
Option 2:
------------
as.data.frame(as.matrix(xdat)*rep(z,each=length(z)))
Option 3:
------------
as.data.frame(t(t(as.matrix(xdat))*z))
Option 4:
------------
as.data.frame(as.matrix(xdat)%*%diag(z))
The suggested solution
as.matrix(xdat)*z
results in
x1 x2 x3
[1,] 2 12 25
[2,] 50 200 500
[3,] 800 3000 6200
and that doesn't seem to be what you want.
Berend
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