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Save data from while loop

Asked by Anonymous User on 5 Jul 2019
Latest activity Edited by madhan ravi
on 5 Jul 2019
How I can save x,y,z data from each irritation and build a matrix ? So I can use them for future work ...
t=0;
while t<100
v=pi/10;
r=6;
dt=0.1;
w=v/r;
t=t+dt;
theta=pi/2;
x=r*sin(theta-w*t)
y=r*cos(theta-w*t)
z=sqrt(10^2-x^2-y^2)
end

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2 Answers

Answer by per isakson
on 5 Jul 2019
Edited by per isakson
on 5 Jul 2019

Your script overwrites x,y,z for each iteration. You need to assign vectors of appropriate length to x,y,z , (preallocate) before running the loop. Try
t=0;
ix=0;
v=pi/10;
r=6;
dt=0.1;
w=v/r;
x = nan(round(100/dt),1);
y = x;
z = x;
while t<100
ix = ix + 1;
t=t+dt;
x(ix)=r*sin(theta-w*t);
y(ix)=r*cos(theta-w*t);
z(ix)=sqrt(10^2-x^2-y^2);
end
Just to learn how to use a loop, despite it is not neccessary in your example.

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madhan ravi
Answer by madhan ravi
on 5 Jul 2019
Edited by madhan ravi
on 5 Jul 2019

You don’t need a loop , simply define t as
t = 0:dt:100;
doc while % to know more about the loop
doc for
and use element wise operation ( https://in.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html ) meaning * to .* and ^ to .^

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