Exponential fit on both gnumeric and openoffice-calc are flawed for small values.

Bug #599534 reported by jacobfe on 2010-06-28
This bug affects 1 person
Affects Status Importance Assigned to Milestone
libio-digest-perl (Ubuntu)

Bug Description

Description: Ubuntu 10.04 LTS
Release: 10.04
gnumeric:1.10.1-1ubuntu1 0
openoffice.org-calc:1:3.2.0-7ubuntu4.1 0

For bothe of these applications the exponential fit is broken. Using the following data plot
0.000568 0.22
0.001136 0.05
0.00170 0.02
0.000136 0.97
0.000329 0.42

Plot and add a trend-line. Make the trend-line exponential and you get a garbage fit. If you multiply column A by 4, the fit works. Multiply by 3 and it fails. It appears that the algorithm used for this type of trend-line is flawed and has limitations that do not occur in MS Excel.

priya (priyamtk) on 2010-07-01
affects: ubuntu → libio-digest-perl (Ubuntu)

Confirmed for gnumeric. I'll have a look at this issue.

Propagated upstream for gnumeric: https://bugzilla.gnome.org/show_bug.cgi?id=633735.

The fix is easy, will be in git within 5 minutes. It would have been fixed much earlier if I had been aware of it.

Awesome! Thanks for fixing!

On 11/01/10 16:07, Jean Bréfort wrote:
> Fixed in gnumeric git:
> http://git.gnome.org/browse/goffice/commit/?id=e1d5d12da829a672a77664ac027984805af13e2a
> Thanks for reporting.

I'd like to say that I don't understand how this bug was attributed to libio-digest-perl. Looks quite weird. I think such bugs should be first opened upstream, unless they are clearly packaging issues. I'll blog about that. OOo guys should probably informed so that they can fix it too.

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