对每行中的不同列执行条件

Question

A = [0,0,1,0,1,0,1,0,0,0;
     0,0,0,0,1,0,1,0,0,0;
     0,0,1,0,1,0,1,0,0,0];

B = [2,5;
     1,6;
     3,10];

预期输出元胞数组：

C = [1,1,1,1;            %// 2-3-4, 3-4-5, 4-5, 5
     0,0,1,1,1,0;        %// 1-2-3, 2-3-4, 3-4-5, 4-5-6, 5-6, 6
     1,1,1,1,1,0,0,0];   %// 3-4-5, 4-5-6, 5-6-7, 7-8-9, 8-9-10, 9-10, 10

矩阵B包括哪些列应该用于执行矩阵A上的条件。例如，B的第一行是2和5；因此应该使用矩阵 A 的第 2 5 列之间的元素来执行条件。 B的第二行是1和6；因此应该使用第 1 列和第 6 列之间的元素来执行条件。等等...

条件：连续3个元素之和大于或等于1则将1写入矩阵C；否则写0。例如A包含0,1,0连续三个元素（和为0+1+0=1），则对矩阵C写1。再如A第二行前三个元素为0 ,0,0（和为0），所以将0写入矩阵C。依此类推...

"Sometimes it can be considered only 1 or 2 successive elements."

比如A的第一行条件执行到第5列结束，那么只考虑第5列的值；这是1。所以1被写入矩阵C。

解释第一行C:

1, since (sum of 2,3,4 elements of A(1,:)) >= 1

1, since (sum of 3,4,5 elements of A(1,:)) >= 1

since max limit is 5, only 2 successive elements are taken here
1, since (sum of 4,5 elements alone of A(1,:)) >= 1

since max limit is 5, only 1 successive element is taken here
1, since (sum of 5th element alone of A(1,:)) >= 1

没有for循环，只有矩阵运算，这么复杂的任务怎么办？或任何技巧？

Answer 1

使用mat2cell, cellfun, im2col and any

subMatLen = 3;

%// Converting both A & B matrix to Cell Arrays to perform operations Row-wise
AC = mat2cell(A,ones(1,size(A,1)),size(A,2));
BC = mat2cell(B,ones(1,size(B,1)),size(B,2));

%// Getting only the columns of each rows within the limits specified  by Matrix B
%// Also appended with zeros for my own convenience as it wont affect the 'summing' process
out = cellfun(@(x,y) [x(y(1):y(2)),zeros(1,subMatLen-1)],AC, BC, 'uni', 0);

%// Finally taking each 1x3 sliding sub-matrix and returning 1 if `any` of it is non-zero
%// which is equivalent to summing and checking whether they are >= 1
out = cellfun(@(x) any(im2col(x, [1,subMatLen], 'sliding')), out, 'uni', 0);

您的示例输入：

A = [0,0,1,0,1,0,1,0,0,0;
     0,0,0,0,1,0,1,0,0,0;
     0,0,1,0,1,0,1,0,0,0];

B = [2,5;
     1,6;
     3,10];

输出：

>> celldisp(out)

out{1} =

 1     1     1     1


out{2} =

 0     0     1     1     1     0


out{3} =

 1     1     1     1     1     0     0     0

如果您希望它们作为单行或单列矩阵，您可以将其添加到代码的底部：

out = cat(2,out{:})

或

out = (cat(2,out{:})).'

对每行中的不同列执行条件

Condition execute for different columns in each row

indexing

matlab

matrix