Apache OpenOffice (AOO) Bugzilla – Issue 48012
Calc: chattype 'interpolated' is missing
Last modified: 2014-02-28 12:46:30 UTC
In calc a chattype 'interpolated' is missing. The 'spline'-type don't satisfy. Look in MS-Excel for it and how it works. It's important for technical dokumentations.
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Could you please give a more detailed description? Are both spline types not sufficient for you? And why not. Which version of Excel do you refer to? Thanks a lot.
Created attachment 34679 [details] XY-diagram with lines only
Created attachment 34680 [details] XY-diagram with cubic spline interpolation
Created attachment 34681 [details] XY-diagram with interpolation issue
For many cases the cubic-spline is fine. I have no Excel at the moment, but I found the oo-clac file in which I had this issue. I made 2 Screenshots and a seperat calc-file in which is only this issue. Please see attechments. Thanks.
Ok, thanks Stefan. I see that the smooth lines in Excel look diffferent from B-Splines or Cubic-Splines. Do you or anybody know how they are calculated in Excel. Or do you or anyone has special expectations for the functions used for calculating the interpolation? Thanks.
With the new parametric method for cubic splines (issue 13699) your example looks much better, but it is not the same as in Excel. You might say that Excel does it still nicer. I've looked a little bit around in the internet. There seems to be no "official" site, which describes the Excel way. But people think, that the way Dr. Brian T. Murphy (Rotating Machinery Analysis, Inc.) does it in his macro solves the problem. The macro is included in the file http://www.xlrotor.com/smooth_curve_bezier_example_file.zip from http://www.xlrotor.com/resources/files.shtml or http://www.xlrotor.com/excel_stuff.htm The description is inside the macro. He writes, that he uses Bézier curves. I have not examined the code yet. The example in the file also works with other 4 points. To run the macro on my German Excel 97 I had to replace the round(something) function with int(something+0.5). Would it be possible legally to adapt that code to OOo?
*** Issue 71735 has been marked as a duplicate of this issue. ***
*** Issue 109228 has been marked as a duplicate of this issue. ***
This Issue requires more information ('needmoreinfo'), but has not been updated within the last year. Please provide feedback as requested and re-test with the the latest version of OpenOffice - the problem(s) may already be addressed. You can download Apache OpenOffice 3.4.1 from http://www.openoffice.org/download Please report back the outcome of your testing, so this Issue may be closed or progressed as necessary - otherwise the issue may be Resolved as Invalid in the future.
Now, after approximately 7 years since the report, I have re-drawn the diagrams in LibreOffice Calc 3.6.4.3 and Excel 2007. I have seens there are now several options in LibreOffice about interpolation. I tried several settings there. Unfortunately no setting draws it as nice as Excel does. For comparison I have attached a screenshot. I have not seen any options about interpolation in Excel. Why are options in LibreOffice necessary? As I have also attached 2006 the data of the diagrams everybody can use them to re-draw the diagrams in any program for other comparisons. So I would only mark this as resolved if the interpolation between Excel and LibreOffice (or OpenOffice; does not matter) look really identical.
Created attachment 80235 [details] Comparison LibreOffice and Excel
Created attachment 82755 [details] Calc 4.1 vs. Excel 2010 Save as xls of attachment 34681 [details]
Created attachment 82756 [details] Smooth lines: Excel 2010 vs. Calc 4.1
Confirmed with AOO410m14(Build:9760) - Rev. 1572807 Rev.1572807 Win 7