In the command window, use a for loop to fill a vector v with the squares of 2, 3, 4, 5.

Question

Albert 2017-10-13

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评论： Albert 2017-10-14

Hi there, I am trying to understand an in class example put am having difficulties completing the code the question is :

In the command window, use a for loop to fill a vector v with the squares of 2, 3, 4, 5. Start with

v = zeros(1,4)

After entering your for loop in the command window, v should be:

>> v 
v=
4 9 16 25

Heres what I have so far:

>> v=zeros(1,4);
i=1;
v(i)=2;
i=2;
v(i)=3;
i=3;
v(i)=4
i=4;
v(i)=5;
v =
       2     3     4     5
  for i=1:4 v=v(i).*v(i); disp(v); end;

however I am getting the message "Index exceeds matrix dimensions."

Can someone offer me some tips with approaching this problem

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Answer 1

Jonathan Chin 2017-10-14

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you are overwriting your vector instead of filling the array

v=zeros(1,4); % this is [0,0,0,0]
v=[2,3,4,5]% pre-assign values

when you index into v with the for loop variable i you overwrite v, see below

for i =1:4
v=v(i).*v(i); %<- this here overwrites your variable v completely on the first loop 
disp(v)%making it 2*2 when i =1, when i becomes 2 there is no longer a second index
end
 %corrected version
  for i =1:4
  v(i)=v(i).*v(i); %<- this here replaces your value at index i
  disp(v)
  end