# Create graphs from a bipartite adjacency matrix

Source:`R/incidence.R`

`graph_from_biadjacency_matrix.Rd`

`graph_from_biadjacency_matrix()`

creates a bipartite igraph graph from an incidence
matrix.

## Usage

```
graph_from_biadjacency_matrix(
incidence,
directed = FALSE,
mode = c("all", "out", "in", "total"),
multiple = FALSE,
weighted = NULL,
add.names = NULL
)
```

## Arguments

- incidence
The input bipartite adjacency matrix. It can also be a sparse matrix from the

`Matrix`

package.- directed
Logical scalar, whether to create a directed graph.

- mode
A character constant, defines the direction of the edges in directed graphs, ignored for undirected graphs. If ‘

`out`

’, then edges go from vertices of the first kind (corresponding to rows in the bipartite adjacency matrix) to vertices of the second kind (columns in the incidence matrix). If ‘`in`

’, then the opposite direction is used. If ‘`all`

’ or ‘`total`

’, then mutual edges are created.- multiple
Logical scalar, specifies how to interpret the matrix elements. See details below.

- weighted
This argument specifies whether to create a weighted graph from the bipartite adjacency matrix. If it is

`NULL`

then an unweighted graph is created and the`multiple`

argument is used to determine the edges of the graph. If it is a character constant then for every non-zero matrix entry an edge is created and the value of the entry is added as an edge attribute named by the`weighted`

argument. If it is`TRUE`

then a weighted graph is created and the name of the edge attribute will be ‘`weight`

’.- add.names
A character constant,

`NA`

or`NULL`

.`graph_from_biadjacency_matrix()`

can add the row and column names of the incidence matrix as vertex attributes. If this argument is`NULL`

(the default) and the bipartite adjacency matrix has both row and column names, then these are added as the ‘`name`

’ vertex attribute. If you want a different vertex attribute for this, then give the name of the attributes as a character string. If this argument is`NA`

, then no vertex attributes (other than type) will be added.

## Details

Bipartite graphs have a ‘`type`

’ vertex attribute in igraph,
this is boolean and `FALSE`

for the vertices of the first kind and
`TRUE`

for vertices of the second kind.

`graph_from_biadjacency_matrix()`

can operate in two modes, depending on the
`multiple`

argument. If it is `FALSE`

then a single edge is
created for every non-zero element in the bipartite adjacency matrix. If
`multiple`

is `TRUE`

, then the matrix elements are rounded up to
the closest non-negative integer to get the number of edges to create
between a pair of vertices.

Some authors refer to the bipartite adjacency matrix as the "bipartite incidence matrix". igraph 1.6.0 and later does not use this naming to avoid confusion with the edge-vertex incidence matrix.

## See also

`make_bipartite_graph()`

for another way to create bipartite
graphs

Other biadjacency:
`as_data_frame()`

## Author

Gabor Csardi csardi.gabor@gmail.com

## Examples

```
inc <- matrix(sample(0:1, 15, repl = TRUE), 3, 5)
colnames(inc) <- letters[1:5]
rownames(inc) <- LETTERS[1:3]
graph_from_biadjacency_matrix(inc)
#> IGRAPH a0b748f UN-B 8 9 --
#> + attr: type (v/l), name (v/c)
#> + edges from a0b748f (vertex names):
#> [1] A--c A--d A--e B--a B--d B--e C--b C--c C--e
```