Re: [Maxima-discuss] dblquad fail

[Doug Stewart]

On Wed, Jul 27, 2016 at 10:32 PM, Doug Stewart <address@hidden> wrote:

On Wed, Jul 27, 2016 at 9:57 PM, Ether Jones <address@hidden> wrote:

Hello.

I am trying to numerically integrate a function using dblquad, but getting errors shown below.  Thank you.

octave-3.6.4.exe:3> I = dblquad(@(r,q)r*sqrt(r^2+1-2*cos(2*pi()*q)),0,1,0,1)
error: for A^b, A must be a square matrix
error: evaluating argument list element number 1
error: called from:
error:    at line -1, column -1
error:    at line -1, column -1
error: quadcc: integrand F must return a single, real-valued vector
error:   K:\OctaveVS\share\octave\3.6.4\m\general\dblquad.m at line 72, column 10
error:    at line -1, column -1
error: quadcc: integrand F must return a single, real-valued vector
error:   K:\OctaveVS\share\octave\3.6.4\m\general\dblquad.m at line 65, column 5

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I don't know what you want, but maybe this will help.

>> I = dblquad(@(r,q)abs( r.*sqrt(r.^2+1-2*cos(2*pi*q))),0,1,0,1)

I =  0.58663

--

DAS

This might also help:

 r=0:.01:1;

 q=0:.01:1;

 [xx yy]=meshgrid(r,q);

 

  ff= @(r,q)abs( r.*sqrt(r.^2+1-2*cos(2*pi*q)))

 zz=ff(xx,yy);

 mesh(xx,yy,zz) # this shows the surface that we are using.

 

 I = dblquad(@(r,q)abs( r.*sqrt(r.^2+1-2*cos(2*pi*q))),0,1,0,1)

--

DAS