[Octave-bug-tracker] [bug #59850] uniquetol missing, so I implemented it

[anonymous]

Follow-up Comment #10, bug #59850 (project octave):

A comment on the sorting suggestion, it is a very good idea for vector data,
when byrows is not true. This is where I started. However, when byrows is true
there will be cases where it could miss duplicates.

An example is trying to remove duplicated points in a Clenshaw Curtis
multidimensional quadrature sparse grid. The points are positioned such that
one and two vector norms along with axis coordinates are the same between
points which can be a significant distance apart so when you sort the data not
all of the points which are almost on top of each other are grouped together
after sorting. The diff function will see a big difference with a point that
is not on top of another and then jump back to the group that is on top of
other points but have a big difference again leaving a duplicate.

To address this issue I tried sorting several different ways but I was still
having difficulties ensuring no duplicates remained. I also did a Google
search and tried out every uniquetol implementation I could find and all I
could find left duplicates. 

So for any algorithm, we implement can I ask that it is able to leave no
duplicates in the sparse grid data. I have attached the difficult data
generator replace my [w,x]=uniquewx(w,x,1e-10); with the uniquetol
implementation or check the sizes of the outputs between the implementations
to ensure we are not leaving duplicates. d and r can be around 4 and the rule
should be Clenshaw Curtis.

Looks like I'm wrong about rows as an input. I've been misreading a call to
unique as uniquetol since I started writing the function.

(file #50765)
    _______________________________________________________

Additional Item Attachment:

File name: squaresparse1dtomd.m           Size:2 KB
    <https://file.savannah.gnu.org/file/squaresparse1dtomd.m?file_id=50765>



    _______________________________________________________

Reply to this item at:

  <https://savannah.gnu.org/bugs/?59850>

_______________________________________________
  Message sent via Savannah
  https://savannah.gnu.org/