I use a formula to calculate values or use set criteria to yield blanks.
Then I graph the data and want the line graph to end where a blank occurs
rather than connect the line to zero where the blank occurs. Actually all
blanks are plotted as zeros, but I could enter -1 instead of blank and make
the scale minimum zero to eliminate this problem if the line did not connect
from the last data point to the -1 or zero.

This problem is not cured by copypaste specialvalues even though the
blanks then no longer contain formula but look indistinguishable from real
blanks. But they do not behave as real blanks, for example, when hitting
enddown arrow.