带多个条件的值 [英] Assign values w/ multiple conditions

问题描述

让我们有一个M = [10 x 4 x 12]矩阵.例如，我使用M(:,:,4):

Let's have a M = [10 x 4 x 12] matrix. As example I take the M(:,:,4):

val(:,:,4) =

     0     0     1     0
     0     1     1     1
     0     0     0     1
     1     1     1     1
     1     1     0     1
     0     1     1     1
     1     1     1     1
     1     1     1     1
     0     0     1     1
     0     0     1     1

如何获取此信息:

val(:,:,4) =

     0     0     3     0
     0     2     2     2
     0     0     0     4
     1     1     1     1
     1     1     0     1
     0     2     2     2
     1     1     1     1
     1     1     1     1
     0     0     3     3
     0     0     3     3

• 如果我在第一列中有1，那么所有随后的1应该是1.
• 如果我在第一列中有0但在第二列中有1，则所有后续的1应该为2.
• 如果我在第一列和第二列中有0，但在第三列中有1，则随后的所有1应该为3.
• 如果我在前三列中有0个，但在第四列中有1个，那么这个应该是四个.
• If I have 1 in the first column then all the subsequent 1's should be 1.
• If I have 0 in the first column but 1 in the second, all the subsequent 1's should be 2.
• If I have 0 in the first and second column but 1 in the third then all the subsequent 1's should be 3.
• If I have 0 in the first 3 columns but 1 in the forth then this one should be four.

注意:逻辑矩阵M的构造如下:

Note: The logical matrix M is constructed:

Tab = [reshape(Avg_1step.',10,1,[]) reshape(Avg_2step.',10,1,[]) ...
    reshape(Avg_4step.',10,1,[]) reshape(Avg_6step.',10,1,[])];

M = Tab>=repmat([20 40 60 80],10,1,size(Tab,3));

推荐答案

这是一种非常简单的方法，适用于2D和3D矩阵.

This is a very simple approach that works for both 2D and 3D matrices.

%// Find the column index of the first element in each "slice".
[~, idx] = max(val,[],2);  

%// Multiply the column index with each row of the initial matrix
bsxfun(@times, val, idx);

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