Hi Neal,
 Thanks for your reply.

dat<-data.frame(x1=1:3,x2=4:6,x3=7:9)
z<-c(0.1,10,100)
#I wanna 0.1*x1,10*x2,100*x3

According to your answer:
> as.matrix(dat)*z
        x1    x2    x3
[1,]   0.1   0.4   0.7
[2,]  20.0  50.0  80.0
[3,] 300.0 600.0 900.0
The above is not what I want.
What I want is:
   x1 x2  x3
1 0.1 40 700
2 0.2 50 800
3 0.3 60 900





 



At 2012-12-31 00:13:33,"Neal H. Walfield" <neal@walfield.org> wrote:
>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

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