# 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

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Alaa Al Miqdadi il 25 Feb 2015
Commentato: Image Analyst il 25 Feb 2015
therefore the answer would be the new vector is 36 6 -18 100 10 0 64 22 -30
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Alaa Al Miqdadi il 25 Feb 2015
Modificato: Geoff Hayes il 25 Feb 2015
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 il 25 Feb 2015
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.

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### Risposte (2)

Image Analyst il 25 Feb 2015
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.
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Greig il 25 Feb 2015
This works on the odd and even indices, is the question not about whether the contents are odd or even?
Image Analyst il 25 Feb 2015
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

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Greig il 25 Feb 2015
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
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