bugGNU Octave - Bugs: bug #44847, extrapolation not available for...

 
 

bug #44847: extrapolation not available for all methods in interp2

Submitted by:  Muhali <muhali>
Submitted on:  Wed 15 Apr 2015 11:25:47 AM UTC  
 
Category: Octave FunctionSeverity: 1 - Wish
Priority: 3 - LowItem Group: Feature Request
Status: Need InfoAssigned to: None
Originator Name: Open/Closed: Open
Release: devOperating System: Any

Add a New Comment(Rich Markup)
   

You are not logged in

Please log in, so followups can be emailed to you.

 

Wed 15 Apr 2015 03:46:13 PM UTC, comment #3:

A parameter EXTRAPVAL is mentioned in the help

"...Note that if EXTRAPVAL is used, METHOD must be specified as well...."

but it is unclear how to use it in the function call, where you only have EXTRAP. Moreover, EXTRAPVAL is never used in the interp2 code itself, but EXTRAP is.

So at least the interp2 documentation is incorrect.

Regarding the linear extrapolation, I mentioned that it used to work until the extrap changeset, so it can easily be revived.

Muhali <muhali>
Wed 15 Apr 2015 03:40:19 PM UTC, comment #2:

See bug #44002 and the fix for that bug, http://hg.savannah.gnu.org/hgweb/octave/rev/5a59c0e1203d.

My reading of that is that the string argument "extrap" is not a Matlab-compatible option and was removed in favor of making the function compatible.

Someone with better understanding of the functions involved can decide whether this can or can't be implemented while staying Matlab compatible, or whether there is a workaround to use for linear extrapolation instead.

Mike Miller <mtmiller>
Project Administrator
Wed 15 Apr 2015 03:24:00 PM UTC, comment #1:

I am not sure I understand the first part of the bug. I ran the following script:

The borders, where no interpolation was possible, are padded with pi. So the EXTRAPVAL is indeed used as intended.

Now about the reason why extrapolation (using 'extrap' or 'pp' as EXTRAPVAL) are not allowed anymore, I don't know. I marked the bug "feature request" for the latter feature that has been removed.

Pantxo Diribarne <pantxo>
Project Member
Wed 15 Apr 2015 11:25:47 AM UTC, original submission:

The interp2 documentation mentions the parameter "EXTRAPVAL", but it is actually never used in the code.

Moreover, interp2 used to work with the option "EXTRAP" as a string for any method. I wonder why this is now limited to splines, although e.g. the linear method is much more "tame".

Muhali <muhali>

 

(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

Attach File(s):
   
   
Comment:
   

No files currently attached

 

Depends on the following items: None found

Items that depend on this one: None found

 

Carbon-Copy List
  • -unavailable- added by mtmiller (Posted a comment)
  • -unavailable- added by pantxo (Posted a comment)
  • -unavailable- added by muhali (Submitted the item)
  •  

    Do you think this task is very important?
    If so, you can click here to add your encouragement to it.
    This task has 0 encouragements so far.

    Only project members can vote.

     

    Please enter the title of George Orwell's famous dystopian book (it's a date):

     

     

    Follow 7 latest changes.

    Date Changed By Updated Field Previous Value => Replaced By
    Wed 15 Apr 2015 03:40:19 PM UTCmtmillerSeverity3 - Normal=>1 - Wish
      Priority5 - Normal=>3 - Low
      StatusNone=>Need Info
      Operating SystemGNU/Linux=>Any
    Wed 15 Apr 2015 03:24:00 PM UTCpantxoItem GroupNone=>Feature Request
      Summaryextrap in interp2=>extrapolation not available for all methods in interp2
    Wed 15 Apr 2015 03:23:59 PM UTCpantxoCategoryNone=>Octave Function

    Back to the top


    Powered by Savane 3.1-cleanup1