如何抑制(不打印)行号？

Question

如何抑制(不打印)行号？
代码如下:

dd<-data.frame(a=gl(2,3),b=gl(3,1,6) ) 
model.matrix( ~a + b + a*b, dd )

尝试:

> dd<-data.frame(a=gl(2,3),b=gl(3,1,6) ) 
> model.matrix( ~a + b + a*b, dd )
  (Intercept) a2 b2 b3 a2:b2 a2:b3
1           1  0  0  0     0     0
2           1  0  1  0     0     0
3           1  0  0  1     0     0
4           1  1  0  0     0     0
5           1  1  1  0     1     0
6           1  1  0  1     0     1
attr(,"assign")
[1] 0 1 2 2 3 3
attr(,"contrasts")
attr(,"contrasts")$a
[1] "contr.treatment"
attr(,"contrasts")$b
[1] "contr.treatment"

> cat(model.matrix( ~a + b + a*b, dd ))
1 1 1 1 1 1 0 0 0 1 1 1 0 1 0 0 1 0 0 0 1 0 0 1 0 0 0 0 1 0 0 0 0 0 0 1
> model.matrix( ~ a + b + a*b, dd )
  (Intercept) a2 b2 b3 a2:b2 a2:b3
1           1  0  0  0     0     0
2           1  0  1  0     0     0
3           1  0  0  1     0     0
4           1  1  0  0     0     0
5           1  1  1  0     1     0
6           1  1  0  1     0     1
attr(,"assign")
[1] 0 1 2 2 3 3
attr(,"contrasts")
attr(,"contrasts")$a
[1] "contr.treatment"
attr(,"contrasts")$b
[1] "contr.treatment"

> dd<-data.frame(a=gl(2,3),b=gl(3,1,6) )
> print(model.matrix( ~a + b + a*b, dd , rowNames=False))
  (Intercept) a2 b2 b3 a2:b2 a2:b3
1           1  0  0  0     0     0
2           1  0  1  0     0     0
3           1  0  0  1     0     0
4           1  1  0  0     0     0
5           1  1  1  0     1     0
6           1  1  0  1     0     1
attr(,"assign")
[1] 0 1 2 2 3 3
attr(,"contrasts")
attr(,"contrasts")$a
[1] "contr.treatment"
attr(,"contrasts")$b
[1] "contr.treatment"

> print(model.matrix( ~a + b + a*b, dd , colNames=False))
  (Intercept) a2 b2 b3 a2:b2 a2:b3
1           1  0  0  0     0     0
2           1  0  1  0     0     0
3           1  0  0  1     0     0
4           1  1  0  0     0     0
5           1  1  1  0     1     0
6           1  1  0  1     0     1
attr(,"assign")
[1] 0 1 2 2 3 3
attr(,"contrasts")
attr(,"contrasts")$a
[1] "contr.treatment"
attr(,"contrasts")$b
[1] "contr.treatment"

Answer 1

不幸的是，在打印矩阵时似乎没有任何方法可以抑制行名称，不是吗？一种选择是强制到 data.frame 并使用row.names的参数print.data.frame()：

dd <- data.frame(a=gl(2,3),b=gl(3,1,6));
print(as.data.frame(model.matrix( ~a + b + a*b, dd )),row.names=F);
##  (Intercept) a2 b2 b3 a2:b2 a2:b3
##            1  0  0  0     0     0
##            1  0  1  0     0     0
##            1  0  0  1     0     0
##            1  1  0  0     0     0
##            1  1  1  0     1     0
##            1  1  0  1     0     1