GNOME Bugzilla – Bug 338626
Implement B-Splines interpolation.
Last modified: 2018-05-22 12:58:53 UTC
More XY chart subtypes are needed, at least similar to Stacked area (both for linear and spline interpolations) and Stacked columns (with 3 alignments of the columns). More general splines are also needed, for smoothing the curve. I want to repeat: Thank you for a great program!
Could you tell us more about what you would like ? Sample images would be great.
Created attachment 64113 [details] PNG image of an example graph with different line types
Comment on attachment 64113 [details] PNG image of an example graph with different line types Sure. Currently Gnumeric can make two types of XY lines in a plot, a straight line connecting the points, and a bezier curve. You can also select if you want the line and/or the points to be shown or not. Other programs oriented on graphical data presentations usually give wider range of the line types. The attached PNG image shows a part of a graph with 3 stepwise connections of the data points with color fill. The difference between the lines is where the step happens: on left point, in the middle, or on right point. Three other lines are different nonlinear curves, Spline, which goes via each point, and b-spline and Bezier, which do not obligatory go through a given point. Usually, these nonlinear lines can also use color fill.
Some comments: * The stepwise connections are straightforward to implement. Just we need some available developer time (a very precious ingredient). * The color fix gives a problem. Currently, we never have more than two fields used in styles. In XY plots, they are marker and line. If we add an area, we need a larger property page. The other way round would be to add the filling as a child, just as it was done for droplines. * The various splines are interesting. IMHO, when they do not go through the points, they are more like trend lines (smoothed curves). There is a framework for that in HEAD. I do not know the maths behind these things, some links (or better, some code) would be welcome. The bezier curves I implemented some times ago are mainly artistic, but not really meaningful.
Created attachment 66173 [details] [review] stepwise connected plots This patch adds 4 new step plots, the three ones requested in this bug and one extra (using (y[i]+y[i+1])/2 as step height. The appropriate icons are already on cvs.
Comment on attachment 66173 [details] [review] stepwise connected plots Hmm, may be the "default-style-has-lines" and "use-spline" properties should remain persistent, otherwise older gnumeric versions will not load properly the new files when there are no lines or for splines
Created attachment 66187 [details] [review] enhanced patch Now, supports invalid data and blank cells.
Created attachment 66197 [details] [review] updated patch with preservation of old properties this one should be secure
Created attachment 66300 [details] [review] patch using a string property to describe the interpolation.
Only B-splines are still missing for this bug, so I rename to make things clear.
*** Bug 698533 has been marked as a duplicate of this bug. ***
-- GitLab Migration Automatic Message -- This bug has been migrated to GNOME's GitLab instance and has been closed from further activity. You can subscribe and participate further through the new bug through this link to our GitLab instance: https://gitlab.gnome.org/GNOME/goffice/issues/6.