At 17:22 09/09/2014 -0700, Nobody Noname wrote:
My earlier example was a simplified version of the data I'm working
with. When Brian & Wdragos technique ...
They were not one technique but two different ones, in fact.
... is applied to the 2026 samples I really have, it sort of works
so I can see what your talking about. I keep altering the
incrementation that takes place in this technique to try to get the
last cell to say the stop time. It comes pretty close but is always
off by a few minutes.
My formula technique will get it right for you. Mr Drago's will also,
provided you do his initial manual calculation correctly. If your
calculation only comes "pretty close", you must be getting something wrong.
The reason for this is there's a limit to the precision you can do
with Times in OpenOffice Calc.
There is always a limit to precision in anything, but this will not
create the problems you describe. (My formula technique is probably
less prone to rounding errors than Mr Drago's repeated addition
method.) There is no reason for any reasonable length of data
sequence that you should notice any rounding errors.
Using the hr/mn/sec format you can't generate small enough
increments to get the generated times to match the stop time. If
there was a hr/mn/sec/fraction of a second format you could do it.
You can format times to show fractions of a second; the normal
precision of numbers in a Calc spreadsheet means that you can
represent times down to around ten fractional places of a second! But
in any case, you are here confusing formatting with the precision of
a number: values are stored to full precision in a cell even if your
cell formatting restricts the display - as it usually will. If you
have a long list of samples, you will need to do Mr Drago's initial
manual calculation to a greater significance than your cell
formatting will perhaps show, or any errors will add up and
eventually show in your list. My formula technique will not suffer
the same problem.
By the way, there is an option at Tools | Options... | LibreOffice
Calc | Calculate | Precision as shown. That causes any calculation to
be performed on the rounded value displayed in any cell instead of
the actual (potentially more accurate) value actually stored in the
cell. Having that ticked would certainly cause rounding errors in Mr
Drago's technique, so you want to have that *not* ticked for normal
spreadsheet use.
In Calc there's a time format that looks like this, but in practice
it doesn't 'roll over' like say minutes or seconds.
Three points here:
o The formats listed are just samples; you can have more fractional
places displayed simply by adding more zeroes to the format code.
o The formats don't affect the calculation, only the display in each
cell (providing you don't have that option above ticked).
o I'm not sure how you think things don't "roll over", but
accumulated fractions of seconds will certainly become seconds,
minutes and even hours when they need to.
It looks like Calc's stock functions won't do the job.
Believe me: my formula works. Mr Drago's does, providing you don't
round the initial result too much. You are welcome to give up trying,
but please don't blame Calc: of course it will "do the job".
I'm thinking of getting around this by finding some source for a
stopwatch program, and maybe modifying it to do something similar,
but with a greater precision of incrementation.
You have about fifteen significant decimal digits in spreadsheet
calculations: that is enough for almost anything, providing you don't
introduce errors yourself.
Why don't you get someone to look at your spreadsheet (or a sample
copy, showing the problem) to see where you are going wrong?
I trust this helps.
Brian Barker
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Context
- [libreoffice-users] Re: Generate a column of times (continued)
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