Trouble is: when I change my nulls to the minimum 25000, this gives me an incorrect result: it plots a false line that plummets to 25000 for all future years when there should be no line at all for the future years (as per the chart in my first post).
I've tried a formula that tests for null values and doesn't add a <set> tag as soon as nulls are encountered, preventing the line from travelling any further. It's basic, but it works for this graph because nulls happen only in the later <set> tags.
Unfortunately, it doesn't work for my 'target' line where the first <set> in the series is a null but later values are not. Although not accurate, I could make this missing 'target' value the same as the 'actual' for this first <set> but want to ask a dumb question first: if I DID make all my null values be my minimum 25000, is there a way I can code a <set> not to be plotted on the graph (ie remain hidden so no line is plotted)?