Question

I am having trouble constructing a unusual lookup formula in Excel.

Normally, I would use VLOOKUP(), but the pitfall is that I want to look up a number in a column from a table that is sorted on an other column. Vlookup can only lookup things on the sorted column itself.

The scenario is as follows:

• The table is sorted ascending on column B.
• For a given parameter P, I now want to find the first A value, starting from the top and going down, that is bigger than or equal to that parameter P.
• The function should then return the corresponding B value.

Table(part off, the complete table is much bigger):

    A      B
1  640    4.5
2  1600   7.0
3  640    7.5
4  1280   12.0
5  1920   16.5
6  2560   21.0
7  1600   19.8
8  3200   26.8
9  4800   33.8

For example, say my parameter is 1100, then I want my formula to return 7.0, because the first entry when searching downwards in column A that is bigger than or equal to 1100 is 1600, which has a corresponding B value of 7.0

I’ve tried my luck with Array Formula’s (also known as “ctrl-shift-enter formula’s”) and constructed something like this:

{=INDEX(table;
        MATCH(MIN(IF(columnA-$C1>=0;columnA;FALSE));
              IF(columnA-$C1>=0;columnA;FALSE);
              0);
        2)}

with C1 containing my parameter, table the range A1:B9, and columnA the range B1:B9

But that doesn’t work (in the example above, it returns 12.0 because 1280 is selected by the MIN() function) .

Solution I don’t want to use:
I could write some VBA could to go through the table, but I don’t want to do that (because of annoying ‘macro warnings’, and because Excel on Mac doesn’t support VBA anymore)

Anybody any clues?

Answer 1

You can use

{=INDEX(B1:B9,MIN(IF(A1:A9>C1,ROW(A1:A9),FALSE)))}

Note that I am using English UK language settings – you will have to alter the formula to match your locale, replacing commas with semi-colons, etc.