A vector is given v=[6, 3, -9, 10, 5, 0, -8, 11, -15]. write a matlab command the doubles the elements that are odd and raises the elements that are even to th power of 2

therefore the answer would be the new vector is 36 6 -18 100 10 0 64 22 -30

[Geoff Hayes]

Alaa - what exactly is your question? This class assignment seems straightforward so you should be able to figure this out using a for loop and if and else block.

[Alaa Al Miqdadi]

v=[6, 3, -9, 10, 5, 0, -8, 11, 15]
i=1;
 for k=1:length(v)
  if rem (v(k),2)==0
  nv(i)=(v(k)^2);
  i=i+1
n=odd(v)
for k=1:n
if v(k)<0  
  v(k)=2*v(k);
end
disp('The new vector is: ')
disp(v)

I did this but I know something is wrong

[Geoff Hayes]

See Greig's answer below for structuring your code. You should be able to simplify it by using an if and else (there is no need for a second for loop, and it is unclear what you expect n=odd(v) to do). Within your loop, as you are doing now, check for even and then let your else handle the case where the number is odd.

Answer 1

[Image Analyst]

If you want to avoid a loop and do it vectorized, try this:

evenIndexes = 2 : 2 : length(v);
oddIndexes = 1 : 2 length(v);
v(evenIndexes) = v(evenIndexes)........you finish it..
v(oddIndexes) = v(oddIndexes)........you finish it..

You already did the formulas in your code so it should be easy to put them in the code above.

[Greig]

This works on the odd and even indices, is the question not about whether the contents are odd or even?

[Image Analyst]

Yeah, after looking at his code more carefully, it looks like you're right. So the code for that would be

oddIndexes = mod(v, 2)
evenIndexes = ~oddIndexes

Answer 2

[Greig]

Your loop structure above seems a little odd and has some missing "end"s. Try this for a basic loop structure...

for k=1:length(v)   
   if % something
      % do something
   else 
      % do something else 
   end
end

And check out

doc even

That should be enough to fix up your code