data.frameがあります
> x
date open high low close volume adjusted
1 2010-01-04 24.52 24.58 23.68 23.71 24192200 23.71
2 2010-01-05 23.75 23.90 22.75 23.30 55649900 23.30
3 2010-01-06 23.25 23.25 22.72 22.90 41214300 22.90
4 2010-01-07 22.90 23.05 22.40 22.65 35533600 22.65
5 2010-01-08 22.50 22.75 22.35 22.60 28854300 22.60
6 2010-01-11 23.50 23.68 22.28 22.60 44284600 22.60
> is.vector(x[,1])
[1] FALSE
> is.vector(x[,2])
[1] TRUE
> is.vector(x[,1])
[1] FALSE
> is.vector(x[,3])
[1] TRUE
> is.vector(x[,4])
[1] TRUE
> is.vector(x[,5])
[1] TRUE
> is.vector(x[,6])
[1] TRUE
> is.vector(x[,7])
[1] TRUE
is.vector(x[,1])
なぜTRUEではないのか知りたいのですが?