how to lapace results

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Brenda Galabe 2018-12-13

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/435488-how-to-lapace-results

评论： Brenda Galabe 2018-12-13

采纳的回答： Walter Roberson

在 MATLAB Online 中打开

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)

采纳的回答

Walter Roberson 2018-12-13

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/435488-how-to-lapace-results#answer_352100

在 MATLAB Online 中打开

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])

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Walter Roberson 2018-12-13

在 MATLAB Online 中打开

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.

Brenda Galabe 2018-12-13