1.8. igraph_layout_grid_fruchterman_reingold — Force based layout generator for large graphs.

1.8. `igraph_layout_grid_fruchterman_reingold` — Force based layout generator for large graphs.

int igraph_layout_grid_fruchterman_reingold(const igraph_t *graph, 
					    igraph_matrix_t *res,
					    igraph_integer_t niter, igraph_real_t maxdelta, 
					    igraph_real_t area, igraph_real_t coolexp,
					    igraph_real_t repulserad, 
					    igraph_real_t cellsize,
					    igraph_bool_t use_seed);

This algorithm is the same as the Fruchterman-Reingold layout generator, but it partitions the 2d space to a grid and and vertex repulsion is calculated only for vertices nearby.

Arguments:

`graph`:	The graph object.
`res`:	The result, the coordinates in a matrix. The parameter should point to an initialized matrix object and will be resized.
`niter`:	Number of iterations to perform.
`maxdelta`:	Maximum distance to move a vertex in an iteration.
`area`:	The area of the square on which the vertices will be placed.
`coolexp`:	The cooling exponent.
`repulserad`:	Determines the radius at which vertex-vertex repulsion cancels out attraction of adjacenct vertices.
`cellsize`:	The size of the grid cells.
`use_seed`:	Logical, if true, the coordinates passed in `res` (should have the appropriate size) will be used for the first iteration.

Returns:

Error code.

Added in version 0.2.

Time complexity: ideally (constant number of vertices in each cell) O(niter*(|V|+|E|)), in the worst case O(niter*(|V|^2+|E|)).