I need a curve fitting algorithm and I like what LO does in ods. Can any one point me to where I can take a look at it, or, send it to me, or, describe it? Most appreciative.
I’m not sure what you mean with “curve fitting algorithm”. Something like the following?
https://opengrok.libreoffice.org/xref/core/chart2/source/view/charttypes/Splines.hxx
https://opengrok.libreoffice.org/xref/core/chart2/source/view/charttypes/Splines.cxx
I’m not sure. I have a graph with 1024 plot values. What I see when I select" lines/lines only" is a pretty with all the individual plot values suppressed. I would like to replicate this graph using the same plot values. I think that when LO outputs a graph, it either selects the points to use, averages the points in some way, or, as you suggest, do something like fitting to a cubic spline. What I was hoping is that there was something I could look at that would describe the process.
Start at Wikipedia, then check your favorite programming language. Regina already gave you the code-pointer for LibreOffice.
You surely mean x-y charts (line type smooth, cubic splines) as mostly generated using Calc?
How would your input be provided to the algorithm?
If the input is a sequence of pairs of coordinates, I would suggest to create a chart in Calc, and to copy the central area of the ouput. You can paste it as a shape (metafile) then into a Draw document (e.g.) and edit it there (not the points, but the shape).
The shape has no area properties. If you need area attributes, place a rectangle behind and group what you get.
The group shape shown on Sheet2 of the attached example document was created this way using the chart inserted in Sheet1.
disask_131743_SplineCurve.ods (47.4 KB)