[vox-tech] spreadsheet question

[Jeff Newmiller]

On Sun, 14 Apr 2002, Peter Jay Salzman wrote:

> is it possible to define a circular reference with a spreadsheet?

Yes.  They don't like it when you do. :)

> consider the equation "t = T * tbar"
> 
> where "t" is time in SI units and tbar is time in some crazy unit system
> which is convenient for my simulation.
> 
> sometimes it's nice to know "what number do i need to input for the
> simulation to run for 3 seconds".  in other words, tbar = t / T is more
> convenient.
> 
> othertimes, it's nice to know "if i input 5 time units into the program,
> how many real seconds would that represent"?   in other words,
> t = T * tbar is more convenient.
> 
> i know i can do this as:
> 
> 
>          A           B         C              D
> 
> 0       'T           9E10
> 1       't           3.0      'tbar           =B1 / B0
> 2       'tbar        5.0      't              =B2 * B0
> 
> 
> 
> what would really be cool is:
> 
> 
>         A              B
> 
> 0      'T             9E10
> 1      't             ?????
> 2      'tbar          ?????
> 
> 
> if i entered data in B1, it would put B1/B0 in cell B2.
> 
> if i entered data in B2, it would put B2*B0 in cell B1.

Sounds like you want a psychic spreadsheet assistant, or a custom data
entry form like the "Edit" button provides in the Financial mode of the
PalmOS Calc application (the blank datum gets calculated).

> this is kind of circular, but definitely has use.  gnumeric is more or
> less compatible with excel.   any spreadsheet gurus out there?
> 
> what would i fill in for the "?????" ?

Whatever formula you typed would vanish the next time you edited the cell
to put in a number to solve in the other direction.

You could set the formula up in one direction use the Tools | Goal
Seek... menu item to reverse the operation.  I think your first solution
above would be easier to use.

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