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

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Sergio Manzetti
Sergio Manzetti 2021-6-22
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
Asvin Kumar
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?

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采纳的回答

Sergio Manzetti
Sergio Manzetti 2021-6-24
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);

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