Only storing final for loop values

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Allison Cicero
Allison Cicero 2019-4-2
回答： Adam Danz 2019-4-3
I am trying to plot t vs I1 and t vs I2, but only the last value of the loop is being stored. I am very new at this so any help would be great
H= [ 0.5*1i -1; -1 -0.5*1i];
psi0= [1; 0];
for n= 1:0.01:10
t=n;
G= expm(-1i*H*t);
psi= G*psi0;
I1= (abs(psi(1,1))).^2;
I2= (abs(psi(2,1))).^2;
end
plot(t,I1)
plot(t,I2)

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采纳的回答

Adam Danz
Adam Danz 2019-4-3
You're overwriting the t, I1 & I2 variables on each iteration. At the end of the loop, you're left with only the final values.
Here is a modification of your code so you that can store the values from each loop.
H= [ 0.5*1i -1; -1 -0.5*1i];
psi0= [1; 0];
n = 1:0.01:10; % Moved outside of the loop
I1 = nan(1,length(n)); %allocate the loop variable
I2 = I1; %allocate the loop variable
for i = 1:length(n) % loop through each value of 'n'
G= expm(-1i*H*n(i)); % reference the i-th value of 'n'
psi= G*psi0;
I1(i)= (abs(psi(1,1))).^2; %store values from each iteration
I2(i)= (abs(psi(2,1))).^2; %store values from each iteration
end
plot(n,I1) %now you have 2 vectors to plot
hold on %don't repace the line you just plot; add to it instead
plot(n,I2)
190403 083838-Figure 1.jpg

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