Error Messages/40756

Warning of missing Index parameter in Sum(X, i) and other array-reducing functions

Error

Example warning dialog:

Cause

The second parameter, index i, is optional in Array-reducing functions, like Sum(X, i), Min(X, i), and so on. But, if X is an array with more than one index (dimension), it is ambiguous which dimension the function should operate over. It may not choose the one the modeler intended.

Remedy

You could click Ignore Warnings to ignore this warning now and in the future.

But, we strongly recommend that you don't because that will make the model behavior hard to predict. Instead, we suggest that you click Edit Definition, and add an explicit index parameter to the function call to avoid this ambiguity. It will make the model much more robust as you or others may add or remove indexes from X in the future.