Many replicate weight matrices have redundant rows, such as when
weights are the same for all observations in a PSU. This function
produces a compressed form. Methods for `as.matrix`

and
`as.vector`

extract and expand the weights.

```
compressWeights(rw, ...)
# S3 method for svyrep.design
compressWeights(rw,...)
# S3 method for repweights_compressed
as.matrix(x,...)
# S3 method for repweights_compressed
as.vector(x,...)
```

## Arguments

- rw
A set of replicate weights or a `svyrep.design`

object

- x
A compressed set of replicate weights

- ...
For future expansion

## Value

An object of class `repweights_compressed`

or a

`svyrep.design`

object with `repweights`

element of class `repweights_compressed`