Going missing

Some calculations involving blank values may give different results to what you might expect. For example, when you pass a blank value into the AND() function, it is treated as TRUE. This is often unhelpful. To make blanks behave in a sensible way in calculations, you must first convert them to be "not available" using NA(). This function takes no inputs, and returns a missing value. To convert a blank value to a missing value, use this pattern.

=IF(ISBLANK(cell), NA(), cell)