My for loop is working but can't plot the out put

Question

feeroz babu 2020-11-16

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/649168-my-for-loop-is-working-but-can-t-plot-the-out-put

回答： Walter iacomacci 2020-11-16

采纳的回答： Mathieu NOE

format long

l=1/2;

u=1/3;

I=[1,0,0;0,1,0;0,0,1];

A=[1,0,0;0,1,0;0,0,1];

%epsilon = input('Enter accuracy (Eps):');

%A=[6,3,1;8,7,5;3,6,2];

%AdjA= [-16,-1,27;0,9,-27;8,-22,18];

G_1=[1/3,0,0;0,1/2,0;0,0,1];

G_2=[1/4,0,0;0,1/5,0;0,0,1/6];

T=[1,0,0;0,1,0;0,0,1];

F=[1/2,0,0;0,1/2,0;0,0,1/2];

i=1;

x(1)=1;

y(1)=1;

z(1)=1;

X_i=[x(i);y(i);z(i)];

for i = 1:100

a_i = 1/i^(1/2);

t = 1/5;

Z_i = X_i-t*[(I-inv(I+l*G_1))*X_i + A*((I-inv(I+u*G_2)))*A*X_i];

i = i+1

X_i = a_i*F*X_i+(1-a_i)*T*Z_i

E = norm(X_i)

n=[3:1:100];

end

plot(n,E)

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Answer 1

Mathieu NOE 2020-11-16

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hello

your E remains a scalar in your code; I assumed it was supposed to be indexed (with i )

so my suggestion below :

format long
l=1/2;
u=1/3;
I=[1,0,0;0,1,0;0,0,1];
A=[1,0,0;0,1,0;0,0,1];
%epsilon = input('Enter accuracy (Eps):');
%A=[6,3,1;8,7,5;3,6,2];
%AdjA= [-16,-1,27;0,9,-27;8,-22,18];
G_1=[1/3,0,0;0,1/2,0;0,0,1];
G_2=[1/4,0,0;0,1/5,0;0,0,1/6];
T=[1,0,0;0,1,0;0,0,1];
F=[1/2,0,0;0,1/2,0;0,0,1/2];
i=1;
x(1)=1;
y(1)=1;
z(1)=1;
X_i=[x(i);y(i);z(i)];
for i   = 1:100
    a_i = 1/i^(1/2);
    t   = 1/5;
    Z_i = X_i-t*[(I-inv(I+l*G_1))*X_i + A*((I-inv(I+u*G_2)))*A*X_i];
    i   = i+1;
    X_i = a_i*F*X_i+(1-a_i)*T*Z_i;
    E(i) = norm(X_i);  % look here
end
n=[3:1:100];
% plot(n,E)
plot(n,E(n))  % and here

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feeroz babu 2020-11-16

Thanks a lot, it works.

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Answer 2

Walter iacomacci 2020-11-16

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https://ww2.mathworks.cn/matlabcentral/answers/649168-my-for-loop-is-working-but-can-t-plot-the-out-put#answer_545688

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Hi Feeroz, I see what you are trying to dom try this:

format long
l=1/2;
u=1/3;
I=[1,0,0;0,1,0;0,0,1];
A=[1,0,0;0,1,0;0,0,1];
%epsilon = input('Enter accuracy (Eps):');
%A=[6,3,1;8,7,5;3,6,2];
%AdjA= [-16,-1,27;0,9,-27;8,-22,18];
G_1=[1/3,0,0;0,1/2,0;0,0,1];
G_2=[1/4,0,0;0,1/5,0;0,0,1/6];
T=[1,0,0;0,1,0;0,0,1];
F=[1/2,0,0;0,1/2,0;0,0,1/2];
i=1;
x(1)=1;
y(1)=1;
z(1)=1;
X_i=[x(i);y(i);z(i)];
E=0;
for i   = 1:100
    a_i = 1/i^(1/2);
    t   = 1/5;
Z_i = X_i-t*[(I-inv(I+l*G_1))*X_i + A*((I-inv(I+u*G_2)))*A*X_i];
i   = i+1
X_i = a_i*F*X_i+(1-a_i)*T*Z_i
E(i) = norm(X_i)
n=[0:1:100];
end
plot(n,E)

Basically I changed only 2 things, added a value for E as 0 before the for loop and added that little E(i) inside the loop which will store the value of norm(X_i) in E on the i position every iteration, if you don't include this you will have a flat value of E and thats why you can't see anything when you plot n vs e. Also changed n size since E and n must have equal sizes so you can plot that otherwise you will have plot error because sizes are different.