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#### Wilba

Wilba said:Magic! Thanks a bunch.

Would you mind talking me through this a little?

Let me see what I can understand. You're comparing the value in each A

cell with the two reference dates.

The "--" looks like a double negation - what is it doing?

OK, I'll answer my own question. It looks like the "--" is doing the

equivalent of DATEVALUE. In the real thing I'm comparing dates directly so I

don't need it anyway. But I can't find any documentation on the "--" ... any

clues?

Does the "*" operator give you a logical "and"?

It's just multiplying 1s and 0s, so in effect, yes.

If the dates are within range you take the values from the corresponding B

cells and give them as both parameters in FREQUENCY. I don't understand

what FREQUENCY gives you when data = bins.

I think I understand this now. You get an array of the number of occurences

of each unique value in the B cells.

Then you're taking the reciprocals and counting them.

Which seems like a perverse way to do it. I prefer to use

SUM(IF(FREQUENCY(...)>0,1)), not because it works any better, but because I

can come back in a month and understand what I'm doing.

I think I'll be able to understand this if I know what "--" is doing, but

more importantly what FREQUENCY does when data = bins.

I think I do now.

Thanks!

Thanks me! :-D