[Octave-bug-tracker] [bug #42037] Missing function integral

[Avinoam Kalma]

Follow-up Comment #8, bug #42037 (project octave):

Thanks for implementing integral.

I have checked integral function on Win-7

All test pass:


>> test integral
PASSES 31 out of 31 tests


Coding style: 
1. In the test code, some of the keywords are given with double quotes
("RelTol") and some with single quotes ('AbsTol')
2. Missing some spaces after commas.

Using Matlab examples -  Is it legal? What about copyright issues?

Problem with Inf:

 
>> fun = @(x) 1./x
fun =

@(x) 1 ./ x

>> a = integral (fun, 0, 1)
warning: quadgk: non finite integrand encountered
warning: called from
    quadgk at line 341 column 7
    integral at line 87 column 7
warning: quadgk: Error tolerance not met.  Estimated error 2.41923
warning: called from
    quadgk at line 397 column 5
    integral at line 87 column 7
a =  38.5083785045586


Matlab result:


>> fun = @(x) 1./x

fun =

  function_handle with value:

    @(x)1./x

>> a = integral (fun, 0, 1)
Warning: Infinite or Not-a-Number value encountered. 
> In integralCalc/iterateScalarValued (line 349)
  In integralCalc/vadapt (line 132)
  In integralCalc (line 75)
  In integral (line 88) 

a =

   Inf


38 is not Inf. Probably the problem is in quadgk and not in integral

What about a simple demo, like:


fun = @(x) cos (x);
integ = @(x) integral (fun, 0, x);
z = [0:0.01:2*pi];
w = arrayfun (integ, z);
plot (z, cos(z), z, w);
title ("integral demo");
h = legend ("f(x) = cos (x)", "integral of f(x)");
legend (h, "location", "southwest");
axis ("tight");
grid on




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