How can I select two out of 6 points for every page without loops?

3 次查看（过去 30 天）
lit
lit 2023-8-10
编辑： Bruno Luong 2023-8-15
I am trying to select two out of 6 points in an array whose size is 6x3xn. These two points are not in the same row on each page as I am trying to select those two of the six points that meet a certain condition. Let's assume that condition is that every coordinate is between 0 and 30.
Is there away to do this without loops?
  8 个评论
显示 6更早的评论
Bruno Luong
Bruno Luong 2023-8-11
编辑：Bruno Luong 2023-8-11
So the number of pages that satisfies that (exactly 2 rows are find) would reduce. And you might keep track of which of those are not discarded, which are.
Your discription "... for every page" "...on each page" are missleading if not wrong.
lit
lit 2023-8-11
编辑：lit 2023-8-11
I'm sorry, I only realized that I don't actually need the pages where not exactly two points are found after writing the question.

请先登录，再进行评论。

请先登录，再回答此问题。

采纳的回答

Jan
Jan 2023-8-10
Ran in:
n = 2;
X = randi(40, 6, 3, n)
X =
X(:,:,1) = 25 18 19 19 23 18 26 5 7 15 39 10 22 35 10 26 35 23 X(:,:,2) = 35 22 6 25 29 2 5 39 5 34 33 36 32 14 17 5 22 33
mask = all(X >= 0 & X <= 30, 2)
mask = 6×1×2 logical array
mask(:,:,1) = 1 1 1 0 0 0 mask(:,:,2) = 0 1 0 0 0 0
Y = reshape(X(cat(2, mask, mask, mask)), [], 3)
Y = 4×3
25 23 7 19 5 25 26 19 29 18 18 2
  6 个评论
显示 4更早的评论
lit
lit 2023-8-15
编辑：lit 2023-8-15
Ran in:
my code now looks like this
X = randi(40,6,3,4)
X =
X(:,:,1) = 12 17 1 32 6 13 35 9 16 2 24 17 20 35 34 10 16 30 X(:,:,2) = 10 3 40 5 30 35 27 22 40 3 35 11 33 29 21 31 7 7 X(:,:,3) = 4 25 17 25 25 8 2 34 4 32 12 25 36 20 7 19 25 32 X(:,:,4) = 10 26 3 33 15 27 19 4 34 2 31 27 30 19 25 12 19 8
mask = all(X>=0 & X<=30,2);
mask(:,:,sum(mask,1)~=2) = 0;
X = permute(X, [2 1 3]);
mask = permute(mask,[2 1 3])
mask = 1×6×4 logical array
mask(:,:,1) = 0 0 0 0 0 0 mask(:,:,2) = 0 0 0 0 0 0 mask(:,:,3) = 1 1 0 0 0 0 mask(:,:,4) = 0 0 0 0 0 0
X = reshape(X(cat(1,mask, mask, mask)),3,[])'
X = 2×3
4 25 17 25 25 8
So now 2 points only on pages where exactly 2 points meet the condition are selected
Sorry in case I have confused you
Bruno Luong
Bruno Luong 2023-8-15
编辑：Bruno Luong 2023-8-15
OK this looks correct. But I don't think you need permute and transpose at all. It seems like a side effect of your though trying to fix Jan's coden but that is not relevant.
n = 4;
nsolperpage = 2;
X = randi(40, [6, 3, n])
mask = all(X >= 0 & X <= 30, 2);
keep = sum(mask,1) == nsolperpage;
extractpages = find(keep)
mask(:,:,~keep) = false;
Y = reshape(X([mask, mask, mask]), nsolperpage, 3, [])

请先登录，再进行评论。

更多回答（1 个）

Bruno Luong
Bruno Luong 2023-8-15
n = 4;
nsolperpage = 2;
X = randi(40, [6, 3, n])
mask = all(X >= 0 & X <= 30, 2);
[~,p] = find(reshape(mask, [], n));
count = accumarray(p, 1, [n 1]);
keep = count == nsolperpage;
extractpages = find(keep)
mask(:,:,~keep) = false;
Y = reshape(X([mask, mask, mask]), nsolperpage, 3, [])

类别

在 Help Center 和 File Exchange 中查找有关 Author Block Masks 的更多信息

标签

产品


版本

R2019b

Community Treasure Hunt

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

Start Hunting!

Translated by