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Title: Another excel question Post by: jimmy_onions on Friday, October 19, 2012, 10:46:20 For all you excel experts, another query which I would have thought would have been ridiculously straight forward, but excel seems to be coming up wanting....
Can you do a basic summation in excel, e.g. the sigma sign..sum of x from x=1 to x=n, where n varies... e.g 1+2+3+4+.....n would have thought this was trivial, but apparently not? Title: Re: Another excel question Post by: Samdy Gray on Friday, October 19, 2012, 10:47:31 Where are you getting 'n' from? A cell value?
Title: Re: Another excel question Post by: jimmy_onions on Friday, October 19, 2012, 10:47:52 yes
Title: Re: Another excel question Post by: Samdy Gray on Friday, October 19, 2012, 10:52:22 And you want to add up all the numbers between 1 and n ?
Title: Re: Another excel question Post by: jimmy_onions on Friday, October 19, 2012, 10:55:01 yep
Title: Re: Another excel question Post by: Samdy Gray on Friday, October 19, 2012, 10:55:43 Use =sum((a1*(a1+1))/2), substitute a1 for the range of the cell where 'n' is stored.
Title: Re: Another excel question Post by: jimmy_onions on Friday, October 19, 2012, 11:04:07 samdy gauss, I mean gray...thanks a lot, that does the trick....what is your mathemtical background that you can pluck out equations like that at a drop of a hat?
That works perfectly for me, however I am still curious if there is a more general summation expression in excel which will work for the summation of any function, not just x, x^2, 3x/2, x^3/x etc etc.. Title: Re: Another excel question Post by: Samdy Gray on Friday, October 19, 2012, 11:09:16 The basic equation for working out the sum of a 1 to n sequence is:
n(n+1) 2 Basic GCSE maths. You could probably use SERIESSUM (http://office.microsoft.com/en-gb/excel-help/seriessum-HP005209253.aspx) but that's more for when it's not exactly a simple series. Title: Re: Another excel question Post by: jimmy_onions on Friday, October 19, 2012, 11:10:56 I did my gcse over 20 years ago...long since forgotten...cheers anyway.
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