Formula to calculate indexes from row and column

• Feb 18th 2008, 01:28 AM
Echilon
Formula to calculate indexes from row and column
This is as much about programming as it is software, but I thought there might be a nifty way to do it with excel that I'm unaware of.

I have two sets of numbers, indexes for rows and columns, and I need to map them to indexes. Rather than actually setting the cell values, I'm trying to get them 'on-the-fly', but I can't get the formula to work.

Eg:
Code:

Row        Col        Index 0        0        0 0        1        1 0        2        2 0        3        3 0        4        4 1        0        5 1        1        6 1        2        7 1        3        8 1        4        9 2        0        10 2        1        11 2        2        12 2        3        13 2        4        14 3        0        15 3        1        16 3        2        17 3        3        18 3        4        19
I need a formula which will always return the index when it's given the row and column, but I can't find one that works.

Here's a spreadsheet if you fancy playing around with it.
• Feb 18th 2008, 05:53 AM
TriKri
5*Row + Col, where 5 = number of columns

To judge from your file, what you have tried to do is:

$index = \left\{\begin{array}{ll}2row+col,&\mbox{ if }
row=0\\2row^2+2+col, & \mbox{ if } row\neq 0\end{array}\right.$

How did you come up with those formulas? :P