peers {Benchmarking} R Documentation

## Find peer firms and units

### Description

The function `peers` finds for each firm its peers, `get.number.peers` finds for each peer the number of times this peer apears as a peer, and `get.which.peers` determines for one or more peers the firms they apear as peers for. Also include a function `get.peers.lambda` to calculate for fimrs the importances (lambdas) of peers.

### Usage

```  peers(object, NAMES = FALSE, N=1:dim(object\$lambda), LAMBDA=0)
get.number.peers(object, NAMES = FALSE, N=1:dim(object\$lambda), LAMBDA=0)
get.which.peers(object, N = 1:dim(object\$lambda), LAMBDA=0)
get.peers.lambda(object,  N=1:dim(object\$lambda), LAMBDA=0)
```

### Arguments

 `object` An object of class Farrell as returned by the functions `dea`, `dea.direct` et al. `NAMES` If true then names for the peers are returned if names are available otherwise the unit index numbers are used. If `NAMES` is a list of names with length equal to the number of units then it is used as names for peers. `N` The firm(s) or peer(s) for which to get the results. `LAMBDA` Minimum weight for extracted peers, i.e. the extracted peers have lambda values larger than `LAMBDA`.

### Details

The returned values are index of the firms and can be used by itself, but can also by used as an index for a variable with names of the firms.

The `peers` returns a matrix with numbers for the peers for each firm; for firms with efficiency 1 the peers are just the firm itself. If there is slack in the evaluation of a firm with efficiency 1, this can be found with a call to `slack`, either directly or by the argument `SLACK` when a function `dea` was called to generate the Farrell `object`.

The `get.number.peers` returns the number of firms that a peer serves as a peer for.

The `get.peers.lambda` returns a list of firms with the peers and corresponding value af lambda.

### Value

The return values are firm numbers. If the argument `NAMES=TRUE` is used in the function `peers` the return is a list of names of the peers if names for the firms are avilable as rownames.

### Note

Peers are defines as firms where the coresponding lambdas are positive.

Note that peers might change between a Farrell object return from `dea` with `SLACK=FALSE` and a call with `SLACK=TRUE` or a following call to the function `slack` because a peer on the frontier with slack might by the call to `dea` be seen as a peer for itself whereas this will not happen when slacks are calculated.

### Author(s)

Peter Bogetoft and Lars Otto larsot23@gmail.com

### References

Peter Bogetoft and Lars Otto; Benchmarking with DEA, SFA, and R; Springer 2011. Sect. 4.6 page 93

`dea`

### Examples

```x <- matrix(c(100,200,300,500,100,200,600),ncol=1)
y <- matrix(c(75,100,300,400,25,50,400),ncol=1)

e <- dea(x,y)
peers(e)
get.number.peers(e)

# Who are the firms that firm 1 and 4 is peers for
get.which.peers(e, c(1,4))
```

[Package Benchmarking version 0.29 Index]