Taking middle 4 values of n size array

32 次查看（过去 30 天）
James Morris
James Morris 2019-8-20
评论： James Morris 2019-8-23
I know how to take the first 4 values of an n size array (1:4)
and the last 4 (end-4:end)
but how would I take the middle 4 values of an n size array no matter the length?
Thanks
  1 个评论
the cyclist
the cyclist 2019-8-20
Do you know if the number of array elements is always even, or always odd? How do you want to define the middle if there are an odd number?

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Jon
Jon 2019-8-20
编辑：Jon 2019-8-20
You could use something like, for an array A
n = length(A(:)) % : treats as column even if this is actually a multidimensional array
midpoint = round(n/2)
select = A(midpoint-1:midpoint+2); % slightly unsymmetrical 1 before, 2 after
Note, you may have to further clarify, what your really mean by "middle 4". There are two sources of asymmetry inherent in taking the "middle 4". If there are an even number of elements then the "middle" one is either closer to one end or the other. Also as you are taking an even number (4) elements then either they are offset one way or the other from the selected middle element
  4 个评论
显示 2更早的评论
Jon
Jon 2019-8-23
Are you still looking for more help with this?
James Morris
James Morris 2019-8-23
Sorry for the late reply. No I figured it out in the end. You guys are awesome, thank you.

请先登录，再进行评论。

更多回答（2 个）

the cyclist
the cyclist 2019-8-20
编辑：the cyclist 2019-8-20
Here is one way, assuming the number of elements is even:
% Input
a = rand(1,8);
numberElements = numel(a);
numberToRemove = numberElements - 4;
numberToRemoveFromEachEnd = numberToRemove/2;
output = a(numberToRemoveFromEachEnd+1:end-numberToRemoveFromEachEnd)
the cyclist
the cyclist 2019-8-20
编辑：the cyclist 2019-8-20
Here is one way, which will work for either even- or odd-length arrays. It is not efficient.
% Input
a = rand(1,9);
whichEnd = 1;
while numel(a) > 4;
a = a(whichEnd:(end+whichEnd-2))
whichEnd = 3-whichEnd;
end
end
It will choose the "slightly left of center" for odd-length array.

类别

在 Help Center 和 File Exchange 中查找有关 Operators and Elementary Operations 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by