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
Alaa Al Miqdadi 2015-2-25
评论： Image Analyst 2015-2-25
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
Alaa Al Miqdadi 2015-2-25
编辑：Geoff Hayes 2015-2-25
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
Geoff Hayes 2015-2-25
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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回答（2 个）

Image Analyst
Image Analyst 2015-2-25
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
Greig 2015-2-25
This works on the odd and even indices, is the question not about whether the contents are odd or even?
Image Analyst
Image Analyst 2015-2-25
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
Greig 2015-2-25
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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