Tool to help reduce adjacency lists for analyzing subsets of maps.

`redist.reduce.adjacency(adj, keep_rows)`

## Arguments

- adj
A zero-indexed adjacency list. Required.

- keep_rows
row numbers of precincts to keep

## Value

zero indexed adjacency list with max value length(keep_rows) - 1

## Examples

```
data(fl25_adj)
redist.reduce.adjacency(fl25_adj, c(2, 3, 4, 6, 21))
#> [[1]]
#> [1] 2 4
#>
#> [[2]]
#> [1] 2 3 4
#>
#> [[3]]
#> [1] 0 1 4
#>
#> [[4]]
#> [1] 1
#>
#> [[5]]
#> [1] 0 1 2
#>
```