A chart series can truncate a couple of datapoints cleanly if you delete the
contents of the desired cells. When you use IF() and return a "" or some
other syntaxes to represent an empty cell, the chart series does not truncate
and your series line deflects to a displayed datapoint value of zero and does
not truncate the series line.
To have a chart truncate a line cleanly and not display erroneous data zero
points and their connecting lines, then we need to find out how to tell a
formula such as the IF function to return a real empty cell to the degree
that the clearcontents method does when you hit the delete key. e.g.
=IF(condition,"",something)
the "" does leave the cell *looking* blank but charts think there is
something there!
Any ideas?