In R, when using named rows, can a sparse matrix column be added (concatenated) to another sparse matrix?

I have two sparse matrices, m1 and m2:

> m1 <- Matrix(data=0,nrow=2, ncol=1, sparse=TRUE, dimnames=list(c("b","d"),NULL))
> m2 <- Matrix(data=0,nrow=2, ncol=1, sparse=TRUE, dimnames=list(c("a","b"),NULL))
> m1["b",1]<- 4
> m2["a",1]<- 5
> m1
2 x 1 sparse Matrix of class "dgCMatrix"

b 4
d .
> m2
2 x 1 sparse Matrix of class "dgCMatrix"

a 5
b .
>

and I want to 开发者_运维问答cbind() them to make a sparse matrix like:

  [,1] [,2] 
a    .    5
b    4    .
d    .    .

however cbind() ignores the named rows:

> cbind(m1[,1],m2[,1])
  [,1] [,2]
b    4    5
d    0    0

is there some way to do this without a brute force loop?

---

You should send the question to Martin Maechler, the author of much of the Matrix package. There is a cBind function, but it does not at the moment recognize rownames, only dimensions, at least as far as I can tell (even when increasing the deparse.level argument to 2).