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Error Handling

 Formula errors are common. If you have a data set with hundreds of records, a divide-by-zero and an #N/A errors are bound to pop up now and then.

In the past, preventing errors required Herculean efforts. Nod your head knowingly if you’ve ever knocked out =IF(ISNA(VLOOKUP(A2,Table,2,0),"Not Found",VLOOKUP(A2,Table,2,0)). Besides being really long to type, that solution requires twice as many VLOOKUPs. First, you do a VLOOKUP to see if the VLOOKUP is going to produce an error. Then you do the same VLOOKUP again to get the non-error result.

Excel 2010 introduced the greatly improved =IFERROR(Formula,Value If Error). I know that IFERROR sounds like the old ISERROR, ISERR, and ISNA functions, but it is completely different.

This is a brilliant function: =IFERROR(VLOOKUP(A2,Table,2,0),"Not Found"). If you have 1,000 VLOOKUPs and only 5 return #N/A, then the 995 that worked require only a single VLOOKUP. Only the 5 VLOOKUPs returned #N/A that need to move on to the second argument of IFERROR.

Oddly, Excel 2013 added the IFNA() function. It is just like IFERROR but only looks for #N/A errors. One might imagine a strange situation where the value in the lookup table is found, but the resulting answer is a division by 0. If you want to preserve the divide-by-zero error for some reason, you can use IFNA() to do this.

A formula of =IFNA(VLOOKUP(),"Not Found") makes sure that you never see a #N/A error.

Of course, the person who built the lookup table should have used IFERROR to prevent the division by zero in the first place. In the figure below, the "n.m." is a former manager’s code for “not meaningful.”

The #DIV/0 error is changed to "n.m." by using =IFERROR(F9/E9,"n.m.")
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