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## [Octave-bug-tracker] [bug #41980] interp1: piecewise linear interpolatio

 From: Mike Miller Subject: [Octave-bug-tracker] [bug #41980] interp1: piecewise linear interpolation with discontinuities behaves differently Date: Thu, 27 Mar 2014 18:43:56 +0000 User-agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20100101 Firefox/17.0

```URL:
<http://savannah.gnu.org/bugs/?41980>

Summary: interp1: piecewise linear interpolation with
discontinuities behaves differently
Project: GNU Octave
Submitted by: mtmiller
Submitted on: Thu 27 Mar 2014 02:43:56 PM EDT
Category: Octave Function
Severity: 3 - Normal
Priority: 5 - Normal
Item Group: Regression
Status: None
Assigned to: None
Originator Name:
Originator Email:
Open/Closed: Open
Discussion Lock: Any
Release: 3.8.1
Operating System: Any

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Details:

This change in behavior may be intentional, please let me know if that's the
case, but it appears like a regression to me.

In 3.6.4, something like the following worked very nicely:

x = [0 0.5 0.5 1]';
y = [0 0 1 1]';
xi = linspace (0, 1, 1000)';
yi = interp1 (x, y, xi);
isequal (yi, [zeros(500,1); ones(500,1)])
ans =  1

This is no longer possible in 3.8. Now the point (0.5,0) is removed from the
input set *before* interpolating, so the resulting line segments are from
(0,0) to (0.5,1) and from (0.5,1) to (1,1). If the "left" option is used, the
point (0.5,1) is removed instead, and the resulting two line segments are now
from (0,0) to (0,0.5) and from (0,0.5) to (1,1).

It looks to me like this changed with the fix for bug #40825, so can Rik or
JuanPi comment on whether this was intentional or an unfortunate side effect?

_______________________________________________________

<http://savannah.gnu.org/bugs/?41980>

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