Create empty 0x0 matrices of varying types

`EmptyMatrix(repr = "C", type = "d")`

- repr
Representation of empty matrix; choose from:

“

`C`

” for a`CsparseMatrix`

“

`T`

” for a`TsparseMatrix`

“

`R`

” for an`RsparseMatrix`

“

`e`

” for an`unpackedMatrix`

“

`d`

” for a dense S3`matrix`

“

`spam`

” for a`spam`

matrix

- type
Type of resulting matrix to return, choose from:

“

`d`

” for numeric matrices“

`l`

” for logical matrices“

`n`

” for pattern matrices

Note, when

`repr`

is “`spam`

”,`type`

must be “`d`

”; when`repr`

is “`d`

”, setting`type`

to “`n`

” returns a logical matrix

A 0x0 matrix of the specified representation and type

```
EmptyMatrix()
#> 0 x 0 sparse Matrix of class "dgCMatrix"
#> <0 x 0 matrix>
EmptyMatrix("spam")
#> <0 x 0 matrix>
#> Class 'spam' (32-bit)
```