is the "for loop" is wrong? what can be the solution?

Question

SAHIL SAHOO 2022-7-20

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1764070-is-the-for-loop-is-wrong-what-can-be-the-solution

评论： SAHIL SAHOO 2022-7-20

采纳的回答： VBBV

clc

ti = 0;

tf = 100E-4;

tspan=[ti tf];

o = 1E6;

tc = 70E-9;

tf = 240E-6;

a1 = 0.02;

a2 = 0.02;

P1 = 1;

P2 = 1;

k = 0.033;

l = 0.5;

f = @(t,y) [ ((y(2)-a1).*y(1)) + k.*(y(1).*cos(y(3))).*(2/tc);

(P1 - y(2).*(1+y(1)))./tf;

o - (k / tc) * 2 * sin(y(3));

];

[T,Y] = ode45(f,tspan,[1;1;0].*10E-3);

% this is the for loop, maybe this is wrong

Y(:,3) = -3:0.01:3;

U = zeros(length(k),1) ;

for i = 1:length(k)

U(i) = -o.*(Y(:,3)) - 2.*(k./tc).*cos(Y(:,3) - pi/2)

end

%plotting the graphs

plot(T,Y(:,3));

xlim([0 10E-5])

xlabel('t')

ylabel('phase difference')

legend('k = 0.033')

plot(Y(:,3),U)

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VBBV 2022-7-20

The for loop code works well as shown in my answer below. which can also be done without a loop.

SAHIL SAHOO 2022-7-20

yeah I mean plot (Y(:,3), U) and the graph is correct too.

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Answer 1

VBBV 2022-7-20

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1764070-is-the-for-loop-is-wrong-what-can-be-the-solution#answer_1011465

编辑：VBBV 2022-7-20

在 MATLAB Online 中打开

clc

ti = 0;

tf = 100E-4;

tspan=[ti tf];

o = 1E6;

tc = 70E-9;

tf = 240E-6;

a1 = 0.02;

a2 = 0.02;

P1 = 1;

P2 = 1;

k = 0.033;

l = 0.5;

f = @(t,y) [ ((y(2)-a1).*y(1)) + k.*(y(1).*cos(y(3))).*(2/tc);

(P1 - y(2).*(1+y(1)))./tf;

o - (k / tc) * 2 * sin(y(3));

];

[T,Y] = ode45(f,tspan,[1;1;0].*10E-3);

% this is the for loop, maybe this is wrong ... yes this assignment is

% incorrect

Y(:,3) = linspace(-3,3,length(Y)); % change this

U = zeros(length(Y),1) ;

for i = 1:length(Y)

U(i) = -o.*(Y(i,3)) - 2.*(k./tc).*cos(Y(i,3) - pi/2); % also this

end

%plotting the graphs

figure(1)

plot(T,Y(:,2));

figure(2)

plot(T,U)

xlim([0 10E-5])

xlabel('t')

ylabel('phase difference')

legend('','k = 0.033')

Warning: Ignoring extra legend entries.

plot(T,U)

You can plot both U and T variables , but for loop needs modififcation

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VBBV 2022-7-20

在 MATLAB Online 中打开

clc

ti = 0;

tf = 100E-4;

tspan=[ti tf];

o = 1E6;

tc = 70E-9;

tf = 240E-6;

a1 = 0.02;

a2 = 0.02;

P1 = 1;

P2 = 1;

k = 0.033;

l = 0.5;

f = @(t,y) [ ((y(2)-a1).*y(1)) + k.*(y(1).*cos(y(3))).*(2/tc);

(P1 - y(2).*(1+y(1)))./tf;

o - (k / tc) * 2 * sin(y(3));

];

[T,Y] = ode45(f,tspan,[1;1;0].*10E-3);

% this is the for loop, maybe this is wrong ... yes this assignment is

% incorrect

Y(:,3) = linspace(-3,3,length(Y)); % change this

U = zeros(length(Y),1) ;

for i = 1:length(Y)

U(i) = -o.*(Y(i,3)) - 2.*(k./tc).*cos(Y(i,3) - pi/2); % also this

end

%plotting the graphs

figure(1)

plot(Y(:,3),U); % i guess you are looking for this

i guess you are looking for this

SAHIL SAHOO 2022-7-20

yes, this graph is correct that what i expected, without for loop I get a straight line.

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Answer 2

Torsten 2022-7-20

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1764070-is-the-for-loop-is-wrong-what-can-be-the-solution#answer_1011635

在 MATLAB Online 中打开

ti = 0;

tf = 100E-4;

tspan=[ti tf];

o = 1E6;

tc = 70E-9;

tf = 240E-6;

a1 = 0.02;

a2 = 0.02;

P1 = 1;

P2 = 1;

k = 0.033;

l = 0.5;

f = @(t,y) [ ((y(2)-a1).*y(1)) + k.*(y(1).*cos(y(3))).*(2/tc);

(P1 - y(2).*(1+y(1)))./tf;

o - (k / tc) * 2 * sin(y(3));

];

[T,Y] = ode45(f,tspan,[1;1;0].*10E-3);

% this is the for loop, maybe this is wrong

U = -o.*Y(:,3) - 2.*(k./tc).*cos(Y(:,3) - pi/2);

%plotting the graphs

plot(T,Y(:,3));

xlim([0 10E-5])

xlabel('t')

ylabel('phase difference')

legend('k = 0.033')

plot(Y(:,3),U)

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