At 12:14 12/02/2015 -0800, Spencer Graves wrote:
I recently noticed that a complicated spreadsheet that had
previously functioned correctly was giving wrong answers without
warning. After the usual wailing and gnashing of teeth, I traced the
problem to a cell containing "=C4-SUM(G11:G1016)". Further
experimentation produced the following simple version of the problem:
(1) Let A1=1, A2=2, and A3=sum(A1:A2); A3 computes here as 3.
(2) Insert cell A1 shift right.
(3) Observe: A3 now computes as 2. This is obvious in this case but
far from obvious in a complicated spreadsheet, where the connection
between A1 and A3 is obscure. In such cases, For an insert that
would cause an error in a reference like A1:A2, I believe that Calc
should issue a warning something like, "WARNING: Insert may change
the answer computed in A3. Do you want to proceed?" I further think
there should be no default and the user should be forced to select
either "Yes" or "No".
Sorry, but I do not see how you can claim that the formula in A3 is
"broken": it remains as =SUM(A1:A2) exactly as you entered it. What
has changed is that you have displaced your data and made the result
of the formula correctly different. I'm glad that Calc has allowed
you to do this. If a spreadsheet program warned you when any
calculated results might change, you would have to confirm just about
every entry or change.
This was observed in LO 22.214.171.124, LO 4..5.0.0.alpha0 2015-02-05
00:36:56, and MS Excel 2003 sp3.
And perhaps in every other spreadsheet ever created?
Should this be filed as a bug report or a feature request?
Neither, I hope.
Wikipedia says, "A software bug is an error, flaw, failure, or fault
in a computer program or system that causes it to produce an
incorrect or unexpected result, or to behave in unintended ways." I
think this fits that definition.
I don't see that the result is incorrect and I'm sure the behaviour
is not unintended. I accept that you see this as an unexpected
result, but then expectation is in the eye of the beholder.
A couple of points:
o Spreadsheets are useful only when the (usually hidden) formulae are
appropriate and there is generally no way to ensure that this is so.
Consequently spreadsheets are a fragile way to construct a means of
computation. This is perhaps unfortunate but nevertheless true.
o One helpful technique might be, after selecting A1 and before
creating the problem by displacing its value, to use Tools |
Detective > | Trace Dependents to show where any dependent formulae
are. This might help you to rethink your change.
I trust this helps.
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