dsolve problem not showing result

Question

Raghuraman S 2019-2-14

0
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https://ww2.mathworks.cn/matlabcentral/answers/444892-dsolve-problem-not-showing-result

编辑： madhan ravi 2019-2-14

I was trying to solve a simple diffrential equation solving dy/dx =y/x and plot curves using different initial value conditions.

Please refer attached picture file, the script throws erros, where as the dsolve function in the command prompt gives the right answer. Matlab code is attached as well. When I change dy/dx = cos(x) or y+x even script works fine.

Sure,I am missing something, usual some help is appreciated.

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Answer 1

madhan ravi 2019-2-14

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https://ww2.mathworks.cn/matlabcentral/answers/444892-dsolve-problem-not-showing-result#answer_360956

编辑：madhan ravi 2019-2-14

在 MATLAB Online 中打开

syms y(x)
eqn = diff(y) == y/x;
vars = y(x);
V = odeToVectorField(eqn)
M = matlabFunction(V,'vars', {'x','Y'})
interval = [0 pi];  %x interval
for y0=-3:4     %initial conditions
[x,ysol]=ode45(M,interval,y0);
plot(x,ysol)
hold on
end
grid on
ysol

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madhan ravi 2019-2-14

Just convert your symbolic ode to numerical ode and then plot the solutions.

Raghuraman S 2019-2-14

编辑：madhan ravi 2019-2-14

Thanks Madhan,

But I got the real problem, I gave y(0) as initial condition in script, which means the solution is always "zero". This was the case in script. When typed in command prompt, I sought general solution where dsolve gave the right result.

In the script when I entered y(1) etc, the solution is just fine. How silly of me!!!!

Anyways, appreciate your reply.

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