# R igraph manual pages

Use this if you are using igraph from R

## Minimum spanning tree

### Description

A subgraph of a connected graph is a minimum spanning tree if it is tree, and the sum of its edge weights are the minimal among all tree subgraphs of the graph. A minimum spanning forest of a graph is the graph consisting of the minimum spanning trees of its components.

### Usage

mst(graph, weights = NULL, algorithm = NULL, ...)


### Arguments

 graph The graph object to analyze. weights Numeric algorithm giving the weights of the edges in the graph. The order is determined by the edge ids. This is ignored if the unweighted algorithm is chosen. Edge weights are interpreted as distances. algorithm The algorithm to use for calculation. unweighted can be used for unweighted graphs, and prim runs Prim's algorithm for weighted graphs. If this is NULL then igraph tries to select the algorithm automatically: if the graph has an edge attribute called weight or the weights argument is not NULL then Prim's algorithm is chosen, otherwise the unweighted algorithm is performed. ... Additional arguments, unused.

### Details

If the graph is unconnected a minimum spanning forest is returned.

### Value

A graph object with the minimum spanning forest. (To check that it is a tree check that the number of its edges is vcount(graph)-1.) The edge and vertex attributes of the original graph are preserved in the result.

### Author(s)

Gabor Csardi csardi.gabor@gmail.com

### References

Prim, R.C. 1957. Shortest connection networks and some generalizations Bell System Technical Journal, 37 1389–1401.

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