# Including codes in a for loop that would store values after each iteration

5 views (last 30 days)
Berke Özsever on 9 Jun 2021
Answered: Ishank Agarwal on 3 Aug 2021
Hello everyone, I am fairly new to matlab so please bear with me although its a fairly fundemental for loop question. The simulink model you see above simulates two robots that try to form a formation thus they exchange their position informations (p1,p2). They robot 1 does its calculations in "compute_u1" where it outputs an updated p1 value, similar with robot 2. Both position vectors p1 and p2 are in the form of [x-coordinate y-coordinate] therefore their sizes are (1x2). Yet since a simulation is ran with a stop time of 40 and a step time of 0.01 the final sizes of each vectors becomes a (4001x2) so, p1-->(4001x2) similarly p2-->(4001x2).
Now I have this for loop:
for n = 1:sample
thisfig = figure();
p1_0 = rand(2,1)*10-5;
p2_0 = rand(2,1)*10-5;
simOut = sim('hetero1d1b');
alldata = simOut.ScopeDataHetero1d1b;
time = alldata.time;
data = alldata.signals;
p1 = data(1).values;
p2 = data(2).values;
x1_total(:,n) = p1(:,1);
y1_total(:,n) = p1(:,2);
x2_total(:,n) = p2(:,1);
y2_total(:,n) = p2(:,2);
end;
basically I ran the simulink model simulation, import the data obtained from it and split the p1 and p2 values into x1,y1,x2,y2 values. But since I have (:,n) on them each variable stores its values after each iteration so if I ran the simulink model with sample=3 I would get x1_total with a size (4001x3).
My problem:
There are serious of calculations which I want to calculate per iteration and I want to be able to store all the values of these calculations so that I can average them out after simulating my models for sample= 3. These calculations are as follows:
alphad2 = 240; %constant value that doesnt get updated
desireddistance = sqrt((p2(:,1)-p1(:,1)).^2+(p2(:,2)-p1(:,2)).^2);
g12 = (p2(:,:)-p1(:,:))./desireddistance;
G12_star = ones(4001,2).* g12_star; %constant value that doesnt get updated
e12b = g12-G12_star
e12bnorm = sqrt(sum(e12b.^2,2))
How can I encorporate these equations in my for loop so that if I ran my simulation for example for n=3 I would have "desireddistance", "g12", "e12b" and "e12bnorm" values store their values per each iteration??? I tried many different versions but either I get a size error or some other error...
I know it's a pretty long one but it's a pretty important matter to me at the moment and I didn't want anyone to have misunderstandings while reading it!

Ishank Agarwal on 3 Aug 2021
Try this:
sample = input('Enter the number of times you want to run the simulation: ');
g12 = zeros(sample, 1); % preallocation of memory as per sample size
e12b = zeros(sample, 1); % preallocation of memory as per sample size
e12bnorm = zeros(sample, 1); % preallocation of memory as per sample size
alphad2 = 240; %constant value that doesnt get updated
G12_star = ones(4001,2).* g12_star; %constant value that doesnt get updated
desireddistance = sqrt((p2(:,1)-p1(:,1)).^2+(p2(:,2)-p1(:,2)).^2);
for i = 1:sample
g12(i, 1) = (p2(:,:)-p1(:,:))./desireddistance;
e12b(i, 1) = g12-G12_star
e12bnorm(i, 1) = sqrt(sum(e12b.^2,2))
end
Thanks

R2021a

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!