union_straight_contours_xld — Compute the union of neighboring straight contours that have a similar
union_straight_contours_xld merges neighboring XLD contours
Contours if certain criteria are fulfilled. At each
iteration, at most two contours that fulfill the given criteria are
merged. The parameter
Iterations controls how often this
step is executed.
Two contours are merged if the shortest distance between their end
points (end points are the projections of the contours' first and
last points onto its regression line) is smaller than
MaxDist, and if the difference in direction (i.e., the
regression lines' direction) is smaller than
If only one of the criteria is fulfilled, the decision on merging can
be influenced by the weighting factor
allows the exceeding of one limit to be balanced by the other value
remaining below the limit by the same amount. The end point
distance is weighted by
Percent, while the directional
difference is weighted by 100 -
This means that two contours are merged if they fulfill the following condition:
If, for example, two contours have an end point distance of 5.0 and
a directional difference of 0.5 (with the limits chosen being
MaxDist = 4.0 and
MaxDiff = 0.625), both
values differ from the limits by 25%. By choosing
Percent = 60%, the larger end point distance is weighted
more than the smaller directional difference, and thus the contours
are not merged. Contrary, if
Percent = 40% is chosen,
the contours are merged.
Percent = 100%, only the end point distance is taken
into account, while for
Percent = 0% only the difference
of direction is used. If
Percent = 50% both criteria
are equally valid.
In case there are parallel contours, there is a danger of merging
neighboring contours. If this is to be avoided,
'noparallel' has to be chosen, while otherwise
'paralleltoo' suffices. For
Mode = 'every', contours are
merged unconditionally. All other parameters have no influence in
The parameters of the regression line are calculated anew for merged contours.
Before the contour parameters can be returned by
get_regress_params_xld, the parameters of the regression
line to the contour must be calculated by calling
Furthermore, note that
union_straight_contours_xld can not compute
the union of contours with different contour point attributes.
This can be the case if different operators are used for the contour
lines_facet). For information
on the contour attributes and when they are defined, see the
respective operator reference. You can query the point attributes of your
Input XLD contours.
Output XLD contours.
Maximum distance of the contours' endpoints.
Default value: 5.0
Maximum difference in direction.
Default value: 0.5
Weighting factor for the two selection criteria.
Default value: 50.0
Should parallel contours be taken into account?
Default value: 'noparallel'
List of values: 'every', 'noparallel', 'paralleltoo'
→(string / integer)
Number of iterations or 'maximum'.
Default value: 'maximum'
Suggested values: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 'maximum'
Typical range of values:
Minimum increment: 1
Recommended increment: 1