Using &"@" with sumproduct and lookupfunctions

[mishh]

I have a spreadsheet where my B column was full of numbers, and my C column was where I checked off which of those numbers needed to be counted. I needed a formula that would give me the total of any number in B where the adjacent cell in C has an "x" in it. So I used this:

=SUMPRODUCT(LOOKUP(C2:C13&"@",{"","x"}&"@",{0,1}),B2:B13)

This formula works great, but I have NO idea why it worked. I copied and pasted the &"@" part from a similar formula I found online and it worked, magically as far as I can tell. I understand how the LOOKUP function is working, and even how the SUMPRODUCT function is using the desired array, I just have no clue what &"@" means. Can anyone help me out??

 

[danzon]

can't answer your question about the "@", but given your example you could just use SUMIF function instead

 

[mishh]

Thanks, Danzon! That's a much more elegant (and simple!) solution. I'll probably use that instead, I didn't even think of SUMIF. But if anyone else can answer my original question anyway, just for curiosity's sake, that'd be great!