[R] How to multiple the vector and variables from dataframe

[Neal H. Walfield]

At Sun, 30 Dec 2012 18:26:45 +0800 (CST),
meng 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 .

You could convert the data frame to a matrix:

> dat=data.frame(x1=1:3, x2=11:13)
> dat
  x1 x2
1  1 11
2  2 12
3  3 13
> as.matrix(dat) * c(3, 2)
     x1 x2
[1,]  3 22
[2,]  4 36
[3,]  9 26

Neal