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# invalid index in program

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shiv gaur el 24 de Feb. de 2022
Cerrada: Rik el 24 de Feb. de 2022
p=8/3;
r=25;
sigma=10;
npoints =5000;
dt = 0.1;
a = zeros(npoints,1);
b = zeros(npoints,1);
c= zeros(npoints,1);
t = zeros(npoints,1);
//t=1:dt:100;
Invalid use of operator.
a(1)=1;
b(1)=1;
c(1)=1;
suma=0;
sumb=0;
sumc=0;
sumS=0;
sumZ=0;
for i = 1:npoints-1
sumS=sumS+a(i)*c(i-npoints);
sumZ=sumZ+a(i)*b(i-npoints);
a(i+1)=((sigma)/(i+1))*(b(i)-a(i));
b(i+1)=(1/(i+1))*(r*a(i)-b(i)-sumS);
c(i+1)=(1/(i+1))*(sumZ-p*c(i));
suma=suma+a(i).*(t^i);
sumb=sumb+b(i).*(t^i);
sumc=sumc+c(i).*(t^i);
t(i+1) = t(i) + dt;
end;
plot(t,suma)
pl revise the program
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shiv gaur el 24 de Feb. de 2022
sorry jan this is edit program that is running program this is the program of lorenz using time step
we have to plan match with below program using power series now program is right
p=8/3;
r=25;
sigma=10;
npoints =500000;
dt = 0.0001;
a = zeros(npoints,1);
b = zeros(npoints,1);
c = zeros(npoints,1);
time = zeros(npoints,1);
a(1)=1;
b(1)=1;
c(1)=1;
for step = 1:npoints-1
a(step+1)=a(step)+sigma*(b(step)-a(step))*dt;
b(step+1)=b(step)+(-a(step)*c(step)+r*a(step)-b(step))*dt;
c(step+1)=c(step)+(a(step)*b(step)-p*c(step))*dt;
time(step+1) = time(step) + dt;
end;
subplot (2,1,1);
plot(time,z,'b' );
xlabel('time');
ylabel('z');
subplot (2,1,2);
plot (x,z,'g' );
xlabel('x');
ylabel('z')
2.power series
p=8/3;
r=25;
sigma=10;
npoints =5000;
dt = 0.1;
a = zeros(npoints,1);
b = zeros(npoints,1);
c= zeros(npoints,1);
t = zeros(npoints,1);
a(1)=1;
b(1)=1;
c(1)=1;
suma=0;
sumb=0;
sumc=0;
sumS=0;
sumZ=0;
for i = 1:npoints-1
sumS=sumS+a(i)*c(i-npoints);
sumZ=sumZ+a(i)*b(i-npoints);
a(i+1)=((sigma)/(i+1))*(b(i)-a(i));
b(i+1)=(1/(i+1))*(r*a(i)-b(i)-sumS);
c(i+1)=(1/(i+1))*(sumZ-p*c(i));
suma=suma+a(i).*(t^i);
sumb=sumb+b(i).*(t^i);
sumc=sumc+c(i).*(t^i);
t(i+1) = t(i) + dt;
end;
plot(t,sumb)
why not giving match plot
Rik el 24 de Feb. de 2022
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Click the link Jan gave you. Also click this.
Feel free to reopen the question and edit your last comment.

### Respuestas (2)

Walter Roberson el 24 de Feb. de 2022
npoints =5000;
for i = 1:npoints-1
sumS=sumS+a(i)*c(i-npoints);
First iteration: i is 1, and a(1) is being indexed; as you initialized a(1) that is valid so far.
Then c(i-npoints) is being indexed. That is c(1-5000) which is c(-4999) which is not a valid index.
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Jan el 24 de Feb. de 2022
Use the debugger to examine the cause of problems. Type this in the command window:
dbstop if error
Run the code again until it stops at the error.
A guess: c(i-npoints) cannot work, because the index is negative.

R2021b

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