Re: [Maxima-discuss] dblquad fail

[address@hidden]

--- octave
> 
> Thank you.
> 
> This works:
> octave-3.6.4.exe:3>  I = dblquad(@(r,q)abs(
> r.*sqrt(r.^2+1-2*cos(2*pi*q))),0,1,0,1)
> I =  0.586626703381746
> 
> ... but this doesn't:
> octave-3.6.4.exe:4>  I =
> dblquad(@(r,q)r.*sqrt(r.^2+1-2*cos(2*pi*q)),0,1,0,1)
> error: quadcc: integrand F must return a single, real-valued vector
> error: called from:
> 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
> 
> Why is the abs() necessary?
> 
perhaps at report some values of r, p, the term in squere root is minus and 
square root of it is imaginary and this causes error.

Tatsuro