force-directed graph layout based on stress majorization with variable constrained

```
layout_with_constrained_stress(
g,
coord,
fixdim = "x",
weights = NA,
iter = 500,
tol = 1e-04,
mds = TRUE,
bbox = 30
)
layout_igraph_constrained_stress(
g,
coord,
fixdim = "x",
weights = NA,
iter = 500,
tol = 1e-04,
mds = TRUE,
bbox = 30,
circular
)
```

- g
igraph object

- coord
numeric vector. fixed coordinates for dimension specified in

`fixdim`

.- fixdim
string. which dimension should be fixed. Either "x" or "y".

- weights
possibly a numeric vector with edge weights. If this is NULL and the graph has a weight edge attribute, then the attribute is used. If this is NA then no weights are used (even if the graph has a weight attribute). By default, weights are ignored. See details for more.

- iter
number of iterations during stress optimization

- tol
stopping criterion for stress optimization

- mds
should an MDS layout be used as initial layout (default: TRUE)

- bbox
constrain dimension of output. Only relevant to determine the placement of disconnected graphs

- circular
not used

matrix of xy coordinates

Be careful when using weights. In most cases, the inverse of the edge weights should be used to ensure that the endpoints of an edges with higher weights are closer together (weights=1/E(g)$weight).

The layout_igraph_* function should not be used directly. It is only used as an argument for plotting with 'igraph'. 'ggraph' natively supports the layout.

Gansner, E. R., Koren, Y., & North, S. (2004). Graph drawing by stress majorization. *In International Symposium on Graph Drawing* (pp. 239-250). Springer, Berlin, Heidelberg.