Hi Mattsies,
concat is defined as:
concat ( [ distinct ] expression, [delimiter [, sort-weight]] )
returns the aggregated string concatenation of all values of expression iterated over a number of records as defined by a group by clause. Each value may be separated by the string found in delimiter. The order of concatenation may be determined by sort-weight. Sort-weight should return a numeric value where the lowest value will render the item to be sorted first. If the word distinct occurs before the expression, all duplicates will be disregarded.
So I think the syntax you used will not return a list of values to iterate over, that's why it causes an error.
Concat is used to e.g. get a comma separated string of values of a dimension like:
concat (DIMENSION, ',')
For example in a Text box or chart expression.
Cheers,
