Bug 53875 - CONFIGURATION: B-spline option in charts wrongly interpolates data instead of smoothing them!
Summary: CONFIGURATION: B-spline option in charts wrongly interpolates data instead of...
Status: RESOLVED WONTFIX
Alias: None
Product: LibreOffice
Classification: Unclassified
Component: Chart (show other bugs)
Version:
(earliest affected)
3.6.0.4 release
Hardware: Other All
: medium normal
Assignee: Not Assigned
URL:
Whiteboard: BSA
Keywords:
Depends on:
Blocks:
 
Reported: 2012-08-21 12:27 UTC by Andy
Modified: 2012-08-29 06:20 UTC (History)
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Description Andy 2012-08-21 12:27:53 UTC
Problem description: in a chart, the B-spline option should produce a composite function that does NOT pass through all given data points (that's the business of the cubic spline), but instead goes through them with a smoothed behaviour. That's what it did until 3.4, and it was quite useful. 
Now since some not totally clear remake of it, it interpolates all data points, just as a normal spline, but it should not do this. 
So now the two options "cubic spline" and B-spline" in the chart options give uselessly equivalent results.
I tried to understand the motivations behind the change in 3.5 documentation but failed. 
Anyway the fact is that a very nice option is totally gone, and you cannot recreate it manually, since the points shown on the chart with this options are not computable through any calc function.
What's worse, if you open old .ods files with such charts and correct b-spline showing, they are automatically updated to the new uncorrect interpolating instead of smoothing version.
Comment 1 Markus Mohrhard 2012-08-29 06:20:28 UTC
The B-Spline algorithm is specified by ODF so we have to implement just what thespecification mentions. There is no chance to implement our own algorithm.