Writing differential equation for plot

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vaibhav gupta 2020-12-5

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评论： vaibhav gupta 2020-12-6

采纳的回答： Ameer Hamza

Can anyone help me how to write differential below equation for plot

d2x/dt2 = -sign(x + dx/dt)

I tried in below way and it is failing

ode = diff(x,t,2) == -sign(x + diff(x,t));

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Ameer Hamza 2020-12-5

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Try this

syms x(t)
d1x = diff(x);
d2x = diff(x,2);
ode = d2x == -sign(x + d1x);
cond = [x(0)==1 d1x(0)==0]
sol = dsolve(ode, cond)

This requires the Symbolic Math toolbox.

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Ameer Hamza 2020-12-6

在 MATLAB Online 中打开

fplot() is used when you want to plot a function handle or s symbolic function. On the other hand, plot() requires x, y data points. To use the plot() function here, you will need to define an x vector and calculate the y-values yourself. fplot() take cares of all these calculations

syms x(t)
d1x = diff(x);
d2x = diff(x,2);
ode = d2x == -sign(x + d1x);
cond = [x(0)==1 d1x(0)==0];
sol = dsolve(ode, cond);
xv = linspace(-5, 5);
yv = subs(sol, t, xv);
plot(xv, yv);