problem with vpa and symsum

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george veropoulos
george veropoulos 2024-11-12，14:58
移动：Stephen23 about 9 hours 前
Hi i make the fumtiom
function z= Escattheory(r,phi)
%UNTITLED Summary of this function goes here
% Detailed explanation goes here
syms kk
[f,N,Nc,a,ra,k0,Z0] = parameter();
E0=1;
Z1=k0.*r;
Z2=k0.*ra;
factor1=besselj(kk,Z2).*besselh(kk,2,Z1)./besselh(kk,2,Z2)
factor2=(-1j).^kk.*cos(kk.*phi)
factor=-E0.*factor1.*factor2.*en(kk);
%z=vpa(symsum(factor,k,0,inf),3)
f_all=symsum(factor,kk,0,300);
y=vpa(f_all,3)
end
when i call the function Escattheory(r,phi) with argument r=ra=1 and phi =0 the resultas is - 1.22 + 5.05e-5i
if i use the sum like this
function z= Escattheory_test(r,phi)
%UNTITLED Summary of this function goes here
% Detailed explanation goes here
Escattheory_test(r,phi)
function y=Escattheory_test(r,phi)
%UNTITLED Summary of this function goes here
% Detailed explanation goes here
[f,N,Nc,a,ra,k0,Z0] = parameter();
E0=1;
Z1=k0.*r;
Z2=k0.*ra;
kk=0:200
factor1=besselj(kk,Z2).*besselh(kk,2,Z1)./besselh(kk,2,Z2)
factor2=(-1j).^kk.*cos(kk.*phi)
factor=-E0.*factor1.*factor2.*e_n(kk);
%z=vpa(symsum(factor,k,0,inf),3)
y=sum(factor)
end
the reuslts is -1-j0 what happen ??
thank you
  2 个评论
Torsten
Torsten 2024-11-12，15:04
编辑：Torsten 2024-11-13，11:11
You forgot to include the parameter function and the e_n (en) function.
george veropoulos
george veropoulos 2024-11-12，15:28
编辑：Torsten 2024-11-13，11:10
thank the parameter function is
function [f,N,Nc,a,ra,k0,Z0] = parameter()
%UNTITLED Summary of this function goes here
c0=3e8;
Z0=120.*pi;
ra=1;
a=0.92;
N=30;
Nc=30;
f=300e6;
lambda=c0./f;
k0=2*pi./lambda;
end
the function e_n is
function y=e_n(k)
if k==0
y=1
elseif k~=0
y=2
end
end
give only numerical value

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采纳的回答

Torsten
Torsten 2024-11-13，11:07
移动：Torsten 2024-11-13，11:09
Ran in:
The numerical bessel functions are not able to compute your sum correctly (for higher values of k, they return NaN) (see below). That's the reason why you get different results.
r = 1;
phi = 0;
Escattheory(r,phi)
Escattheory_test(r,phi)
factor =
Columns 1 through 9 -0.4406 - 0.0000i 0.0000 - 0.4248i -0.5758 + 0.0000i 0.0000 - 0.0582i -0.6314 - 0.0000i 0.0000 + 0.7456i 0.5554 + 0.0000i 0.0000 - 0.3150i -0.1466 + 0.0000i Columns 10 through 18 0.0000 + 0.0582i 0.0203 - 0.0000i 0.0000 - 0.0063i -0.0018 + 0.0000i -0.0000 + 0.0005i 0.0001 - 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i Columns 19 through 27 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 - 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 - 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i Columns 28 through 36 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i -0.0000 - 0.0000i Columns 37 through 45 -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 - 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i Columns 46 through 54 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i Columns 55 through 63 0.0000 + 0.0000i -0.0000 - 0.0000i -0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i Columns 64 through 72 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i -0.0000 - 0.0000i Columns 73 through 81 -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i Columns 82 through 90 -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 - 0.0000i 0.0000 + 0.0000i Columns 91 through 99 0.0000 - 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i Columns 100 through 108 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i Columns 109 through 117 -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i Columns 118 through 126 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i Columns 127 through 135 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i Columns 136 through 144 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i Columns 145 through 153 -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i Columns 154 through 162 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i Columns 163 through 171 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i Columns 172 through 180 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i Columns 181 through 189 -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i Columns 190 through 198 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i Columns 199 through 207 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i Columns 208 through 216 0.0000 - 0.0000i -0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i 0.0000 + 0.0000i Columns 217 through 225 0.0000 + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i Columns 226 through 234 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi Columns 235 through 243 NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i Columns 244 through 252 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi Columns 253 through 261 NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i Columns 262 through 270 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi Columns 271 through 279 NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i Columns 280 through 288 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi Columns 289 through 297 NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i Columns 298 through 301 0.0000 + NaNi NaN + 0.0000i 0.0000 + NaNi NaN + 0.0000i
ans = NaN + NaNi
function z= Escattheory(r,phi)
%UNTITLED Summary of this function goes here
% Detailed explanation goes here
syms kk
[f,N,Nc,a,ra,k0,Z0] = parameter();
E0=1;
Z1=k0.*r;
Z2=k0.*ra;
factor1=besselj(kk,Z2).*besselh(kk,2,Z1)./besselh(kk,2,Z2);
factor2=(-1j).^kk.*cos(kk.*phi);
factor=-E0.*factor1.*factor2.*e_n(kk)
%z=vpa(symsum(factor,k,0,inf),3)
f_all=symsum(factor,kk,0,300);
z=vpa(f_all,3);
end
function y=Escattheory_test(r,phi)
%UNTITLED Summary of this function goes here
% Detailed explanation goes here
[f,N,Nc,a,ra,k0,Z0] = parameter();
E0=1;
Z1=k0.*r;
Z2=k0.*ra;
kk=0:300;
factor1=besselj(kk,Z2).*besselh(kk,2,Z1)./besselh(kk,2,Z2);
factor2=(-1j).^kk.*cos(kk.*phi);
factor=-E0.*factor1.*factor2.*en(kk)
%z=vpa(symsum(factor,k,0,inf),3)
y=sum(factor);
end
function [f,N,Nc,a,ra,k0,Z0] = parameter()
%UNTITLED Summary of this function goes here
c0=3e8;
Z0=120.*pi;
ra=1;
a=0.92;
N=30;
Nc=30;
f=300e6;
lambda=c0./f;
k0=2*pi./lambda;
end
function y=en(k)
if k==0
y=1;
else
y=2;
end
end
function y=e_n(k)
y = piecewise(k==0,1,k~=0,2);
end
  13 个评论
显示 11更早的评论
Torsten
Torsten 2024-11-14，12:37
编辑：Torsten 2024-11-14，13:11
As said, I don't know precisely why "piecewise" works with the symbolic solution while your if-construct gives a wrong answer.
My guess is that your function "e_n" is called with a symbolic (unspecified) variable (kk) that is not identified as "0" (which would give 1 for y), but as "else" (which always gives 2 for y).
But you might want to contact MATLAB support for a definite answer:
https://uk.mathworks.com/support/contact_us.html
george veropoulos
george veropoulos 2024-11-14，15:41
thank! i sent a report about this in matlab

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