EXTRACT2 - Access to contents of memory storage operators

Several operators - 


contain a graph describing the relation between two or more variables. Various operations on the data in the graph may be of interest.

Access to information within the operators is provided through an EXTRACT2 function. The format is

    EXTRACT2({Node}, Control@, LISTLINK(List matching parameters))


Node is the variable connected to the operator whose data is to be extracted (note that the node is delivered within a list, making it switchable).

Control@ is a logical control - unless True, EXTRACT2 does nothing.

The parameter list varies for the different operators being accessed.


The variables in the list correspond (in order) to the dimension variables of the histogram. A 'LIST' matching one of the dimensions will cause a list of values corresponding to that dimension to be output.

A variable matching the output of the HISTOGRAM can be used to produce a list whose members match the output condition. Some alternatives

UKE - a UKE constant is ignored.

0 - all items in a dimension which have a zero entry are output.

20<-> 50 - all items in another dimension which have entries in this range are output.


Variable1, Variable2... are variables matching the dimensions of the relation. The values on these variables, rather than any values active on the relation, will be used to access the cells in the relation.
Option$ describes the particular value to be returned.