How to plot coupling functions?

Question

Toshith Vats 2021-6-8

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/850810-how-to-plot-coupling-functions

评论： Toshith Vats 2021-6-11

Want to plot these coupling functions r(t) and p(t) (in image) on a graph. I tried using this code and ended up with a blank graph(without errors) . Kindly help. Please note t varies as 2 to 3 with stepping of 0.01 .

z1 = -1.0629;
z2 = 0.5948;
%Code for r(t)
r_int1 = @(s) (2/3 - s).^(-1/2) .* (6 + abs(r(s))+abs(p(s))) ./ (5.*exp(s+4).*(1+abs(r(s))+abs(p(s))));
r_int2 = @(s) (t-s).^(-1/2) .* (6+abs(r(s))+abs(p(s))) ./ (5*exp(s+4).*(1+abs(r(s))+abs(p(s))));
r = @(t) ( z1.*t.^(-1/3)/gamma(1/2) .* integral(r_int1, 0, 2/3) ) + ( (1/gamma(1/2)) .* integral(r_int2, 0, t) );
%Code for p(t)
p_int1 = @(s) (3/2 - s).^(-4/5) .* (1/exp(2*s)) .* (sin(r(s))+sin(p(s))); 
p_int2 = @(s) (t - s).^(-4/5) .* (1/exp(2*s)) .* (sin(r(s))+sin(p(s)));
p = @(t) ( z2.*t.^(-3/2)/gamma(1/5) .* integral(p_int1, 0, 3/2) ) + ( (1/gamma(1/5)) .* integral(p_int2, 0, t) );
fp = fplot(r,p,[2 3]);
fp.Marker = '*';

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Cris LaPierre 2021-6-8

Without seeing your code, it's hard to say why your plot was empty.

Toshith Vats 2021-6-8

Kindly check now I have upated

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Answer 1

Cris LaPierre 2021-6-8

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https://ww2.mathworks.cn/matlabcentral/answers/850810-how-to-plot-coupling-functions#answer_719780

在 MATLAB Online 中打开

If I don't use fplot, I do get a more descriptive error message. Based on the code you have shared, you are using your function handle r in you computation of r_int1 and r_int2 before it has been defined.

z1 = -1.0629;
z2 = 0.5948;
%Code for r(t)
r_int1 = @(s) (2/3 - s).^(-1/2) .* (6 + abs(r(s))+abs(p(s))) ./ (5.*exp(s+4).*(1+abs(r(s))+abs(p(s))));
r_int2 = @(s) (t-s).^(-1/2) .* (6+abs(r(s))+abs(p(s))) ./ (5*exp(s+4).*(1+abs(r(s))+abs(p(s))));
r = @(t) ( z1.*t.^(-1/3)/gamma(1/2) .* integral(r_int1, 0, 2/3) ) + ( (1/gamma(1/2)) .* integral(r_int2, 0, t) );
%Code for p(t)
p_int1 = @(s) (3/2 - s).^(-4/5) .* (1/exp(2*s)) .* (sin(r(s))+sin(p(s))); 
p_int2 = @(s) (t - s).^(-4/5) .* (1/exp(2*s)) .* (sin(r(s))+sin(p(s)));
p = @(t) ( z2.*t.^(-3/2)/gamma(1/5) .* integral(p_int1, 0, 3/2) ) + ( (1/gamma(1/5)) .* integral(p_int2, 0, t) );
% fp = fplot(r,p,[2 3]);
% fp.Marker = '*';
plot(r(2:.01:3),p(2:0.01:3))
Unrecognized function or variable 'r'.

Error in solution (line 5)
r_int1 = @(s) (2/3 - s).^(-1/2) .* (6 + abs(r(s))+abs(p(s))) ./ (5.*exp(s+4).*(1+abs(r(s))+abs(p(s))));

Error in integralCalc/iterateScalarValued (line 314)
                fx = FUN(t);

Error in integralCalc/vadapt (line 132)
            [q,errbnd] = iterateScalarValued(u,tinterval,pathlen);

Error in integralCalc (line 75)
        [q,errbnd] = vadapt(@AtoBInvTransform,interval);

Error in integral (line 87)
Q = integralCalc(fun,a,b,opstruct);

Error in solution (line 7)
r = @(t) ( z1.*t.^(-1/3)/gamma(1/2) .* integral(r_int1, 0, 2/3) ) + ( (1/gamma(1/2)) .* integral(r_int2, 0, t) );