Subscript Updimensioning

[JamesPHoughton]

When a multidimensionally subscripted variable (say with 2 dimensions) is a function of a subscripted variable with fewer (say 1) dimension, Vensim will broadcast the lower dimensional array over all values of the new dimension.
(See https://github.com/SDXorg/test-models/tree/master/tests/subscript_updimensioning for an example). Xarray does not do this by default, so we'll need to extend the functionality.

This has special relevance for subscripted stocks that are initialized with floats.

This could be a bigger task...

[JamesPHoughton]

This is also an issue when a subscripted variable takes its value from another variable returning only a float. This means we'll probably have to deal with the updimensioning at runtime, not just translate time, which is a pain. For an example, see: https://github.com/SDXorg/test-models/tree/master/tests/subscript_constant_call

[JamesPHoughton]

This is also the primary issue preventing success of: https://github.com/SDXorg/test-models/tree/master/tests/subscript_mixed_assembly

[JamesPHoughton]

This is going to require a function to be aware of the dimensions it should put out. In the past, we have had a dimension dictionary as an attribute of the subscripted function. This is probably something we shouldreturn to.