This function creates a two- or three-columns `data.frame`

where
each row represents the interaction between two nodes (site and species for
example) and an optional third column indicating the weight of the
interaction (if `weight = TRUE`

) from a contingency table (sites as
rows and species as columns for example).

## Usage

```
mat_to_net(
mat,
weight = FALSE,
remove_zeroes = TRUE,
include_diag = TRUE,
include_lower = TRUE
)
```

## Arguments

- mat
a contingency table (i.e.

`matrix`

).- weight
a

`boolean`

indicating if the value are weights.- remove_zeroes
a

`boolean`

determining whether interactions with weight equal to 0 should be removed from the output.- include_diag
a

`boolean`

indicating whether the diagonal should be included in the output. Only for squared matrix.- include_lower
a

`boolean`

indicating whether the lower triangular matrix should be included in the output. Only for squared matrix.

## Value

A `data.frame`

where each row represents the interaction
between two nodes and an optional third column indicating the weight of the
interaction.

## Author

Maxime Lenormand (maxime.lenormand@inrae.fr), Pierre Denelle (pierre.denelle@gmail.com) and Boris Leroy (leroy.boris@gmail.com)