connectGroups - creates links with a specified pattern between groups

### USAGE

        connectGroups <group-list1> (<group-list>)* [-projection <proj-type> |
            -strength <strength> | -mean <mean> | -range <range> |
            -type <link-type> | -bidirectional]

### DESCRIPTION

This command creates sets of links between groups. Each group in group-list1 will project to each group in the second group list. Those in the second list will project to those in the third and so on. By default this creates a full projection, but several patterns of sparse projections may also be specified.

Possible projection types (or connectivity patterns) are FULL, UNLESIONED, RANDOM, FIXED_IN, FIXED_OUT, FAIR, FAN, and ONE_TO_ONE. These may be abbreviated by any unique prefix. For sparse patterns, the strength is a floating point number in the range [0,1] specifying the density of the connectivity, as described below. It must be specified for all of the sparse patterns, but not for FULL or ONE_TO_ONE.

In describing the projection types, S is the specified connectivity strength, I is the number of units in the sending group, O is the number of units in the receiving group and f() is the floor function.

FULL creates the dense projection from each sending unit to all receiving units. This is the default.

UNLESIONED is like FULL but only creates connections between healthy, unlesioned units in the two groups. This can be used to create a partial projection.

RANDOM simply connects each pair of pre- and post-synaptic cells with probability S.

FIXED_IN ensures that each postsynaptic unit receives exactly f(S*I) inputs. The number of outputs from a given presynaptic unit may vary.

FIXED_OUT ensures that each presynaptic unit has exactly f(S*O) outputs.

FAIR ensures that each sending unit will have exactly f(S*O) outputs and each receiving unit will have either floor or ceiling of (I*f(S*O) / O) inputs.

FAN causes each input unit to project to the f(S*O) outputs that are closest to it. The closeness measure wraps around the ends of the arrays.

ONE_TO_ONE connects each unit in the sending group to the corresponding unit in the receiving group. The two groups need not have the same number of units; one link will be formed for each unit in the smaller of the two groups. For one-to-one connections, the mean defaults to 1.0 and the range defaults to 0.0. The weights are frozen by default.

If range or both mean and range are given, they will determine the parameters used for randomizing weights in this projection. If left unspecified, the network defaults will be used for these links.

By default the links in the new projection will have a type with the same name as the sending group. This can be overridden by specifying a different link type.

The -bidirectional flag will cause a projection to be formed in the reverse direction whenever one is formed in the forward direction.

### EXAMPLES

To create a full projection (of type "input") from group "input" to group "hidden" which uses range -1.0+/-0.5 when randomizing weights in this projection:

        lens> connectGroups input hidden -mean -1.0 -range 0.5

To create bidirectional FAIR projections between groups "in" and "hid1", "in" and "hid2", "hid1" and "out", and "hid2" and "out" with approximately 50% of the possible connections and with each link having type "t1":

        lens> connectGroups in {hid1 hid2} out -bi -p FAIR -s 0.5 -type t1

### SEE ALSO

addGroup, connectGroupToUnits, connectUnits, elmanConnect, addLinkType, disconnectGroups, setLinkValues

Last modified: Wed Nov 15 11:12:30 EST 2000