Round to nearest odd integer

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Caleb
Caleb on 13 Aug 2012
Edited: Walter Roberson on 30 Dec 2019
Does MATLAB have a function to round numbers to the nearest odd integer?
  1 Comment
Walter Roberson
Walter Roberson on 14 Aug 2012
Do you want negative numbers handled the same way? e.g., -1/3 rounded to -1 ?

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Accepted Answer

Matt Fig
Matt Fig on 13 Aug 2012
Edited: Matt Fig on 13 Aug 2012
I don't think so, but you could make your own:
function S = round_odd(S)
% round to nearest odd integer.
idx = mod(S,2)<1;
S = floor(S);
S(idx) = S(idx)+1;
  2 Comments
Sean de Wolski
Sean de Wolski on 13 Aug 2012
I think you meant:
idx = mod(S,2)<1 %note < not <=
Otherwise it returns evens for S = magic(5);
Matt Fig
Matt Fig on 13 Aug 2012
Yeah, I caught that one too. I like Babak's better anyway, LOL.

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More Answers (4)

Babak
Babak on 13 Aug 2012
Edited: Walter Roberson on 30 Dec 2019
Not that I know of.. but you can use this:
function y=fun(x)
y = 2*floor(x/2)+1;
end
depending on what you want to do with the even numbers you can ether use floor or ceil in the above function.
  2 Comments
mirza
mirza on 29 Dec 2019
That's an efficient approach, but its better to use "round" function instead of "floor" or "ceiling" function. In floor case, the error may occur for rounding numbers to Even.
For example.
If the number is " 23.7227731 "
then statement => 2*floor(x/2) will provide answer "22"
However,
the statement => 2*round(x/2) will provide answer "24"
Walter Roberson
Walter Roberson on 30 Dec 2019
2*floor(23.7227731/2)+1 would be 23, and 23.7227731 has indeed been rounded to the nearest odd number.
2*round(23.7227731/2)+1 would be 25, but 25-23.7227731 is about 1.67 which is greater than 23.7227731-23 ~= 0.72 . Therefore 23 is the closest odd number, to 23.722773, and 25 is not the closest odd number.
I would therefore suggest to you that round() does not solve the problem posed by the original poster.

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Azzi Abdelmalek
Azzi Abdelmalek on 13 Aug 2012
a=7.8; %example
round((a-1)/2)*2+1
  3 Comments
mirza
mirza on 29 Dec 2019
True, the function "round" is better option instead of functions "floor" or "ceiling" as suggested in thread. In floor case, the error may occur for rounding numbers to Even.
For example.
If the number is " 23.7227731 "
then statement => 2*floor(x/2) will provide answer "22"
However,
the statement => 2*round(x/2) will provide answer "24"

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gerit
gerit on 12 Sep 2018
Edited: Walter Roberson on 15 Sep 2018
x-mod(x,2)+1
even numbers will be rounded up

Gimantha Upasena
Gimantha Upasena on 21 Apr 2015
Edited: Gimantha Upasena on 21 Apr 2015
In matlab what is the method to take the values of a matrix and round them off to the nearest even number?..... meaning 2.1 should be rounded off to 2 and also 2.8 should also be rounded off to 2 because if rounded off to 3 ...3 is an odd number so it's not accepted.
  1 Comment
Walter Roberson
Walter Roberson on 30 Dec 2019
Edited: Walter Roberson on 30 Dec 2019
floor(x/2)*2
which should work for both positive and negative numbers.

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