[R] Check values in colums matrix

[Gabor Grothendieck]

Try sd(obj.tr) which will give a vector of standard deviations, one per column.
A column's entry will be zero if and only if all values in the column
are the same.

On 8/24/06, Muhammad Subianto <msubianto at gmail.com> wrote:
> Dear all,
> I apologize if my question is quite simple.
> I have a dataset (20 columns & 1000 rows) which
> some of columns have the same value and the others
> have different values.
> Here are some piece of my dataset:
> obj <- cbind(c(1,1,1,4,0,0,1,4,-1),
>             c(0,1,1,4,1,0,1,4,-1),
>             c(1,1,1,4,2,0,1,4,-1),
>             c(1,1,1,4,3,0,1,4,-1),
>             c(1,1,1,4,6,0,1,5,-1),
>             c(1,1,1,4,6,0,1,6,-1),
>             c(1,1,1,4,6,0,1,7,-1),
>             c(1,1,1,4,6,0,1,8,-1))
> obj.tr <- t(obj)
> obj.tr
> > obj.tr
>     [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9]
> [1,]    1    1    1    4    0    0    1    4   -1
> [2,]    0    1    1    4    1    0    1    4   -1
> [3,]    1    1    1    4    2    0    1    4   -1
> [4,]    1    1    1    4    3    0    1    4   -1
> [5,]    1    1    1    4    6    0    1    5   -1
> [6,]    1    1    1    4    6    0    1    6   -1
> [7,]    1    1    1    4    6    0    1    7   -1
> [8,]    1    1    1    4    6    0    1    8   -1
> >
>
> How can I do to check columns 2,3,4,6,7 and 9 have
> the same value, and columns 1,5 and 8 have different values.
>
> Best, Muhammad Subianto
>
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