At Sun, 30 Dec 2012 16:28:44 +0000,
Andrius Druzinis wrote:
>
> Hi Neal,
>
> Notice that c(2, 3) gets replicated into c(2, 3, 2, 3, 2, 3) and then
> multiplied by column. This is not the same as multiplying each column by
> the respective element in vector c(2, 3).
I think you mean multiplied by element.
Here's a better solution using t to transpose the matrix:
dat=data.frame(x1=1:3, x2=11:13)
as.matrix(dat)
x1 x2
[1,] 1 11
[2,] 2 12
[3,] 3 13
t(as.matrix(dat)) * c(2, 3)
[,1] [,2] [,3]
x1 2 4 6
x2 33 36 39
>
> Andrius
>
>
> 2012/12/30 Neal H. Walfield <n...@walfield.org>
>
> > 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
> >
> > ______________________________________________
> > R-help@r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> > http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
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