On Mar 13, 2010, at 6:30 PM, Hyo Lee wrote:
Hi guys,
I have a very simple question.
I'm trying to make multiple columns to a single column.
For example,
*ttx1* is a 46*72 matrix.
so, I tried this.
*d1=ttx1[,1]
d2=ttx1[,2]
...
d72=ttx1[,72]*
now, d1, d2, ...,d72 become a 46*1 matrix.
And then.. I tried..
*dd=rbind(d1, d2, ..., d72)*
I thought *dd* should be 3312*1 matrix; but it becomes 72*46.
I really wanted to make it a single column (3312*1).
> ttx1 <- matrix(1:3312, ncol=46)
> str(ttx1)
int [1:72, 1:46] 1 2 3 4 5 6 7 8 9 10 .
It is as easy as applying the c() function:
> str( c(ttx1) )
int [1:3312] 1 2 3 4 5 6 7 8 9 10 ...
Well maybe only a vector. (as.vector would have done the same thing,
or if you really want a one column matrix then ...)
> dim(ttx1) <- c(3312,1)
> str(ttx1)
int [1:3312, 1] 1 2 3 4 5 6 7 8 9 10 ...
Matrices in R are basically vectors anyway. Their dim attributes let
matrix like operations get done but they remain vactors underneath.
Do you know what is wrong in this code?
This code gave you a vector rather than a one column matrix: d1=ttx1[,
1], since dimensions that are 1 get dropped by default. The only way
to keep the result as a column matrix would be to use the drop=FALSE
argument to "[":
> d1=ttx1[,1, drop=FALSE]
> d2=ttx1[,2, drop=FALSE]
> str(rbind(d1,d2))
int [1:144, 1] 1 2 3 4 5 6 7 8 9 10 ...
Or, do you have a better idea in
making multiple columns to a single column?
David Winsemius, MD
West Hartford, CT
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