Cubic-splines cause non-function progess graphs, use B-Spline instead
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
Weight Tracker ODS |
Fix Released
|
High
|
Jon Thysell |
Bug Description
The progress chart of my weight log showed a measured weight curve that was not a function of the time, looping and backtracking. This is due to the automatic smoothing in the ProgressChart graph, which uses cubic-splines. See attached screenshot 1.
This behaviour is fixed by un-protecting the cell, right-clicking on the weight line, "Chart Type"/"Smooth Line Properties" and checking "B-spline" instead of "Cubic splines": B-splines are an approximation of a real-value function from R to R, hence respect the "no-backtrack on X-axis", while cubic-splines are an of a parametrized curve from R to R^2, not guaranteeing the "no-backtrack on X-axis".
See attached screenshot 2.
Dataset causing problem was having a whole 15 days of missing data due to holidays:
85.0
Empty
85.0
Empty
84.0
84.2
Empty
84.1
83.8
83.3
82.8
82.4
81.5
81.8
82.3
82.1
Then 16 Empty entries
83.1
81.6
82.0
81.9
81.7
81.4
Related branches
Changed in wtods: | |
status: | New → Confirmed |
importance: | Undecided → High |
assignee: | nobody → Jon Thysell (jonthysell) |
milestone: | none → 2.2.3 |
status: | Confirmed → Triaged |
Changed in wtods: | |
status: | Triaged → Fix Committed |
Changed in wtods: | |
status: | Fix Committed → Fix Released |
Additional precision: B-splines of order > 1 do not pass exactly by the points, on the countrary to the cubic spline approximation. Even so, I'd rather have a non-smoothed measured weight curve than a time-travelling curve, since the other curve gives the smoothed trend anyways.