Error using Contour: input arguments must be numeric or objects which can be converted to a double

Question

Sergio Manzetti 2021-6-22

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/862230-error-using-contour-input-arguments-must-be-numeric-or-objects-which-can-be-converted-to-a-double

回答： Sergio Manzetti 2021-6-24

Hi, I have the given code where I try to plot levels curves of the givenfunction

syms r x y k z
[ph,r] = meshgrid((0:5:360)*pi/180,0:.5:10);
[X,Y] = pol2cart(ph,r);
Z = X+i*Y;
J = besselj(k,l.*r);
J2 = besselj(k,m.*r);
Y = bessely(k,l.*r);
Y2 = bessely(k,m.*r);
H = besselh(k,r);
F1 = symsum((J).*exp(1i*k*ph),k,-5,5);
F2 = symsum((J2+Y2).*exp(1i.*k.*ph),k,-5,5);
F3 = symsum(H.*exp(1i.*k.*ph),k,-5,5);
pwu = nan(size(F1), 'like', F1);
mask = 0 <= r & r < 0.5;
pwu(mask) = F1(mask);
mask = 0.5 <= r & r < 1;
pwu(mask) = F2(mask);
mask = r >= 1;
pwu(mask) = F3(mask);
U = subs(pwu, {l, m}, {1.5, 3});hold on
contour(X,Y,imag(double(U)),30)
axis equal
xlabel('r','FontSize',14);
ylabel('phi','FontSize',14);

But I get an error for the 4th last line. How can this be made in a way it is converted to a double?

Thanks!

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Asvin Kumar 2021-6-24

I'm not able to run this script because the variables l, m, n, etc are not defined. Could you update the attached code so that your error can be reproduced?

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Sergio Manzetti 2021-6-24

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/862230-error-using-contour-input-arguments-must-be-numeric-or-objects-which-can-be-converted-to-a-double#answer_732590

在 MATLAB Online 中打开

Yes, here it is, working script

syms r x y k z l m
[ph,r] = meshgrid((0:5:360)*pi/180,0:.5:10);
[x,y] = pol2cart(ph,r);
Z = x+1i*y;
J = 0.9426656*besselj(k,l.*r);
J2 = 0.640840882*besselj(k,m.*r);
Y = bessely(k,l.*r);
Y2 = 0.4361500838*bessely(k,m.*r);
H = 1.1159118143*besselh(k,r);
F1 = symsum((J).*exp(1i*k*ph),k,-5,5);
F2 = symsum((J2+Y2).*exp(1i.*k.*ph),k,-5,5);
F3 = symsum(H.*exp(1i.*k.*ph),k,-5,5);
pwu = nan(size(F1), 'like', F1);
mask = 0 <= r & r < 0.5;
pwu(mask) = F1(mask);
mask = 0.5 <= r & r < 1;
pwu(mask) = F2(mask);
mask = r >= 1;
pwu(mask) = F3(mask);
U = subs(pwu, {l, m}, {1.5, 3});hold on
w=double(U)
contour(x, y, angle(double(U)), 30);
axis equal
xlabel('r','FontSize',14);
ylabel('phi','FontSize',14);