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Re: quadl crashes on evaluation
From: |
Ben Abbott |
Subject: |
Re: quadl crashes on evaluation |
Date: |
Sat, 20 Sep 2008 06:13:02 -0400 |
On Sep 19, 2008, at 11:46 PM, rmcd wrote:
I find that using quadl in Cygwin Octave 3.0.2-1 crashes octave,
dumping me
at the prompt.
Let y=f(x) where f(x) = x .* sin (1 ./ x) .* sqrt (abs (1 - x));
(This is the example from p. 272 of the 3.0.2 manual)
v=quad ("f",0,3) % produces the result 1.9819.
v=quadl("f",0,3) % crashes cygwin 3.0.2, generates numerous errors in
Ubuntu 3.0.0
Am I doing something wrong or is there a problem with quadl in this
case?
Thanks!
Bob
When you say "crash" what do you get, exactly?
I get the following errors repeated many times
error: evaluating binary operator `+' near line 169, column 3
error: evaluating binary operator `+' near line 170, column 3
error: evaluating binary operator `+' near line 171, column 3
error: evaluating binary operator `+' near line 172, column 3
error: evaluating binary operator `+' near line 173, column 3
error: evaluating assignment expression near line 168, column 7
error: evaluating if command near line 157, column 3
error: called from `quadl:adaptlobstp' in file `/Users/bpabbott/
Development/Octave Toolbox/quadl/quadl.m'
error: evaluating assignment expression near line 126, column 5
error: called from `quadl' in file `/Users/bpabbott/Development/Octave
Toolbox/quadl/quadl.m'
error: evaluating assignment expression near line 14, column 3
Looking in quadl.m we have
x = [a, m-x1*h, m-alpha*h, m-x2*h, m-beta*h, m-x3*h, m, m+x3*h, ...
m+beta*h, m+x2*h, m+alpha*h, m+x1*h, b];
y = feval (f, x, varargin{:});
When called, the first element of "x" is zero, thus your function
returns a NaN.
If your function is modified
f(x) = x .* sin (1 ./ (x+eps)) .* sqrt (abs (1 - x));
and an integration tolerance is added
v = quadl ('f' ,0, 3,. 0001)
v = 1.9818
If any event, please describe what you mean by "crash".
Ben
- quadl crashes on evaluation, rmcd, 2008/09/19
- Re: quadl crashes on evaluation,
Ben Abbott <=
- Re: quadl crashes on evaluation, rmcd, 2008/09/20
- Re: quadl crashes on evaluation, David Bateman, 2008/09/20
- Re: quadl crashes on evaluation, rmcd, 2008/09/20
- Re: quadl crashes on evaluation, Ben Abbott, 2008/09/20
- Re: quadl crashes on evaluation, Ben Abbott, 2008/09/20
- Re: quadl crashes on evaluation, rmcd, 2008/09/20