Reading data from an excel sheet. A1 is “foo”, A2 is blank. B1 is =A1, which evaluates to “foo”, and B2 is =A2, which evaluates to 0. If you want to aggregate according to column B, you have to compare 0 and “foo”.
You have an excel sheet with various unknown data types which can be a string, a number or a formula that needs evaluation? And you don't check types of variables before comparing them? In that case I would argue that you fall into the category "not know what you are doing", because checking the type would be the first needed thing. That is the very first situation in which it is needed in fact...
Reading data from an excel sheet. A1 is “foo”, A2 is blank. B1 is =A1, which evaluates to “foo”, and B2 is =A2, which evaluates to 0. If you want to aggregate according to column B, you have to compare 0 and “foo”.