# My code keeps coming up with "Index Exceeds Array Bounds" help?

조회 수: 1(최근 30일)
댓글: Madison Goodwin 2018년 4월 30일
n = 0;
t = 0;
deltat = 0.1;
m = 0.44;
Cd = 0.05;
p = 1.29;
Ra = 0.135;
%Find b using the rearranged formula for circumference of a circle.
b = 0.6/(pi()*2);
A = pi()*Ra*b;
% Pre set random values for testing code
x = [12,12,12];
deltat = [0.1];
agravity = [0,0,-9.81];
v = [2,2,2];
vwind = [3,1,2];
vdrag = [2,1,2];
fdrag = [3,2,3];
while x<=100
n = n + 1;
t(n+1) = t(n) + deltat;
x(n+1) = x(n) + v(n).*deltat;
v(n+1) = v(n) + (agravity(n).*deltat);
end

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### 답변(1개)

Walter Roberson 2018년 4월 30일
You have
agravity = [0,0,-9.81];
so agravity is length 3. You are not storing new agravity entries as you go along like you are for t, x, v, so when you reach n = 4, agravity(n) will be an error.
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So I want to create arrays for each variable such that its got x,y,z quantities. So I have to create a loop that iterates over each value in the array. But I also need to include in that the time is also changing in the loop, and I don't know how? But ive got this so far. Where: t = 0 n = 0 deltat = 0.1,
x = [], v = [], fdrag = [], vwind = [], vdrag = [], agravity= []
while x<=100
n = n + 1;
t(n+1) = t(n) + deltat;
x(n+1) = x(n) + (v(n).*deltat);
% Finding Acceleration including other forces
vdrag = v(n) - vwind(n);
Magfdrag = norm(fdrag(n));
Magfdrag(n) = 0.5*p*A*Cd.*(norm(vdrag(n))).^2;
fdrag(n+1) = Magfdrag(n).*(-vdrag(n)/norm(vdrag(n)));
atotal(n+1) = agravity(n) + (fdrag(n)./m);
v(n+1) = v(n) + (atotal(n).*deltat);
end

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