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And lo on Fri, 09 May 2008 22:42:05 +0100, Chambers
<bdc### [at] yahoo com> did spake, saying:
> So I have a certain function f(x), where x is a positive integer value.
>
> I would like another function g(y) which is the sum of all values of
> f(x), with x ranging from 0..y
>
> This is trivial using Sigma notation. Unfortunately, this is not
> available in
> any spreadsheet I know of (I use MS Office at work, and OpenOffice.org at
> home).
I think the assumption is that anyone who knows Sigma notation will
already know both the geometric and arithmetic progression formulas.
> I'd rather not write a macro for this,
[snip]
How would you input the x value into the function? if you had your
M*R*(D^x) then had a GEOPROG(lower, upper, step, formula) how would you
write the formula containing the variable x in a way Excel (or any
spreadsheet) could interpret?
> Not to mention that every time I opened the spreadsheet, I'd have to
> deal with those annoying security warnings about dangerous macros.
Yes annoying, but understandable that user-defined functions trigger the
macro security flag. Though if it's something you're going to use a lot
then you could just sign it and add the signature as a trusted source.
> I could populate an entire column on a separate sheet with the values I
> need,
Yes unfortunately that's what the Excel SERIESSUM formula requires, and it
wouldn't work for you anyway as the formula equivalent is sum(x*(D^x))
where x is the range.
--
Phil Cook
--
I once tried to be apathetic, but I just couldn't be bothered
http://flipc.blogspot.com
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