how to lapace results
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Brenda Galabe
on 13 Dec 2018
Commented: Brenda Galabe
on 13 Dec 2018
how to plot this please
deqdiff = 'diff(y(t),t,t) + y(t) - cos(t)'
ldeqdiff = laplace(deqdiff,t,s)
sldeqdiff = subs(ldeqdiff,{'D(y)(0)','y(0)'},{1,1})
syms Ys
ldeqinit = subs(sldeqdiff,'laplace(y(t),t,s)',Ys)
ly = solve(ldeqinit,Ys)
ilaplace(ly,s,t)
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Accepted Answer
Walter Roberson
on 13 Dec 2018
syms s t y(t)
Dy = diff(y);
deqdiff = diff(y(t),t,t) + y(t) - cos(t);
ldeqdiff = laplace(deqdiff,t,s);
sldeqdiff = subs(ldeqdiff,{Dy(0), y(0)},{1,1});
syms Ys
Lyt = laplace(y(t), t, s);
ldeqinit = subs(sldeqdiff, Lyt, Ys);
ly = solve(ldeqinit,Ys);
ily = ilaplace(ly,s,t);
fplot(ily, [0 20])
4 Comments
Walter Roberson
on 13 Dec 2018
You are using the transition release, when fplot had been introduced but did not yet support symbolic expressions.
Replace
fplot(ily,[0 20])
with
Fily = matlabFunction(ily);
fplot(Fily, [0 20])
.... And laplace still is not documented in your release (or any other release) as accepting a character vector. You need to start using documented behaviour or else we are going to start telling you to work things out by yourself since you are relying on undocumented behaviour.
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