https://bugs.documentfoundation.org/show_bug.cgi?id=110993
stragu <[email protected]> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |[email protected] | |.org --- Comment #25 from stragu <[email protected]> --- Created attachment 176554 --> https://bugs.documentfoundation.org/attachment.cgi?id=176554&action=edit side-by-side LibreOffice and R graphs for 2^n cubic spline I have a very limited understanding of cubic splines, but I feel like this might be "not a bug". I have tested building a cubic spline with R and plotting it with ggplot2 for comparison with what LibreOffice does. Attached is the result: both plots look the same. The R code makes sure similar axis breaks are used. 500 values were interpolated to build the spline curve, using the spline() function and the method "normal". R's spline() functions has various methods available. Most of them (fmm, periodic, natural) will generate negative values to fit a spline to this data. However, one method (hyman) will only generate values above 0 and be visualised in the hockey stick look (i.e. shooting up only towards the end, after the x = 80 mark). As I understand it, LibreOffice's cubic spline smoother uses a normal cubic spline, whereas xghost was expecting a different kind. Arguably, the exact kind of interpolation used should be properly documented in our help pages. xghost, are you able to produce a comparison with a different tool, or a reference that supports that LibreOffice's calculation is fundamentally wrong? -- You are receiving this mail because: You are the assignee for the bug.
