Modifying odd/even numbers of a column vector

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How would I go about modifying the odd and even elements of the following vector ?
x = [4 5 7 6 5 8 2 1];
So that when run it can carry out either +,-,*,/,^ ?.
Also after the vectors have been changed the disp(x); shows all all elements, including ones not changed.

Accepted Answer

Rik
Rik on 24 Feb 2021
If you have trouble with Matlab basics you may consider doing the Onramp tutorial (which is provided for free by Mathworks).
x = [4 5 7 6 5 8 2 1];
%with simple indexing:
x(1:2:end)=2*x(1:2:end);
disp(x);
8 5 14 6 10 8 4 1
%or with logical indexing with mod:
L=mod(x,2)==0;
x(L)=2*x(L);
disp(x);
16 5 28 12 20 16 8 1

More Answers (1)

Hernia Baby
Hernia Baby on 24 Feb 2021
Edited: Hernia Baby on 24 Feb 2021
You can modyfiy each element with mod function.
x = [4 5 7 6 5 8 2 1];
x_odd = x(mod(x,2)==1); % odd element
x_even = x(mod(x,2)==0); % even element
mod
  3 Comments
Rik
Rik on 24 Feb 2021
Note that you made a small typo: you should have used == to compare the output of mod to 1 or 0.
Hernia Baby
Hernia Baby on 24 Feb 2021
Thank you, Rik! I will modify my typo.
--------------------------------
To Matt
I got what you want to do.
Then, you can do this with logical indexing.
It is same with Rik's code.
times = 2;
x = [4 5 7 6 5 8 2 1];
idx_odd = mod(x,2) == 1; % odd element
x(idx_odd) = times * x(idx_odd);
disp(x);

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