R语言中将向量按照行生成数据框

> a <- c(2,5,6,7)
> b <- c(6,3,2,9)
> c = rbind(a,b)
> c
  [,1] [,2] [,3] [,4]
a    2    5    6    7
b    6    3    2    9
> class(c)
[1] "matrix" "array" 
> c <- data.frame(c)
> c
  X1 X2 X3 X4
a  2  5  6  7
b  6  3  2  9
> class(c)
[1] "data.frame"