# Help with For-Loop question?

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I keep getting the same error, about not being any real or logical answer.

here is the question; Create a time vector x = 0:2*pi. Using a for-loop, plot ten different curves on the same graph where the first curve is x1 = sin(x), the second curve is x2 = sin(x1), the third curve is x3 = sin(x2) and so on. Note that by using a for-loop it is not necessary to create ten separate variables to solve this problem.

Here is what I've been entering

x=0

>> for i=[pi/5:pi/5:2*pi]

x(i)=sin(x(i-(pi/5)))

end

??? Attempted to access x(0); index must be a positive integer or logical.

Any help would be appreciated

##### 0 Comments

### Accepted Answer

Robert
on 5 Oct 2011

N=10;

x=zeros(N,numel(pi/5:pi/5:2*pi));

x(1,:)=pi/5:pi/5:2*pi;

for j=2:N

x(j,:)=sin(x(j-1,:));

end

plot(x(1,:),x')

##### 0 Comments

### More Answers (1)

Walter Roberson
on 5 Oct 2011

t = 0:pi/5:2*pi;

curvenums = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];

for K = 1 : numel(curvenums)./size(curvenums,1)

if ~curvenum(K)

x(:,curvenum(K+1)) = sin(t);

else

x(:,curvenum(K+1)) = sin(x(:,curvenum(K)));

end

end

plot(t,x)

##### 2 Comments

Robert
on 5 Oct 2011

Walter Roberson
on 5 Oct 2011

The posting is clearly a homework assignment. The code I provided is functional but would get no marks from any marginally alert marker as it would obviously not be written by the student. It is code that can be learned from but not profitably cloned as the assignment answer.

Straight forward and readily understood solutions, on the other hand, are fodder for student copying without any real understanding.

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