subtraction of each row with every other row

2 次查看（过去 30 天）
ST
ST 2020-12-8
回答： Paul Hoffrichter 2020-12-9
I want to subtract each row of the matrix with every other row and store it in a different bigger size matrix, for example-
A=[1,2,3:4,5,6:7,8,9];
B[1-4,2-5,3-6; 1-7,2-8,3-9; 4-1,5-2,6-3; 4-7,5-8,6-9; 7-1,8-2,9-3; 7-4,8-5,9-6];
That means if the original matrix is of size 3×3 then the answer matrix would be 6×3.
My original matrix is of size 40×150.
  3 个评论
显示 1更早的评论
ST
ST 2020-12-8
That was a typo, apology. Thanks for your efforts though.
Paul Hoffrichter
Paul Hoffrichter 2020-12-8
Could you fix up your OP removing any typos, and show the desired results.

请先登录，再进行评论。

请先登录，再回答此问题。

回答（2 个）

Paul Hoffrichter
Paul Hoffrichter 2020-12-9
B = repmat(A, N,1) - repelem(A,N,1);
Paul Hoffrichter
Paul Hoffrichter 2020-12-8
编辑：Paul Hoffrichter 2020-12-8
A=[1,2,3,4,5; 6,7,8,9,10; 11, 12, 13, 14, 15;16, 17, 18, 19, 20];
c = nchoosek(1:size(A, 1),2);
c2 = [c; fliplr(c)];
B = zeros( length(c2), size(A,2));
for ii = 1: size(c2,1)
[r1 r2] = deal( c2(ii,1), c2(ii,2) );
B(ii,:) = A(r1,:) - A(r2,:);
end
B
B =
-5 -5 -5 -5 -5
-10 -10 -10 -10 -10
-15 -15 -15 -15 -15
-5 -5 -5 -5 -5
-10 -10 -10 -10 -10
-5 -5 -5 -5 -5
5 5 5 5 5
10 10 10 10 10
15 15 15 15 15
5 5 5 5 5
10 10 10 10 10
5 5 5 5 5
  3 个评论
显示 1更早的评论
Paul Hoffrichter
Paul Hoffrichter 2020-12-8
编辑：Paul Hoffrichter 2020-12-8
I kept the numbers more manageable to compare results.
METHOD_ONE = 0
N=20;
step=50;
N=3;
step=4;
rng(10);
A=randi(5*N, N, step);
if METHOD_ONE
c = nchoosek(1:size(A, 1),2);
c2 = [c; fliplr(c)];
B = zeros( length(c2), size(A,2));
for ii = 1: size(c2,1)
[r1 r2] = deal( c2(ii,1), c2(ii,2) );
B(ii,:) = A(r1,:) - A(r2,:);
end
else
B=zeros(N*N,step);
count=1;
jj=1:(N*N);
n=N;
for ii=1:N
rowNums = jj(count:count+n-1);
B( rowNums ,:) = A - A(ii, :);
count=count+N;
end
end
A
B
Output:
METHOD_ONE =
0
A =
12 12 3 2
1 8 12 11
10 4 3 15
B =
0 0 0 0
-11 -4 9 9
-2 -8 0 13
11 4 -9 -9
0 0 0 0
9 -4 -9 4
2 8 0 -13
-9 4 9 -4
0 0 0 0
METHOD_ONE =
1
A =
12 12 3 2
1 8 12 11
10 4 3 15
B =
11 4 -9 -9
2 8 0 -13
-9 4 9 -4
-11 -4 9 9
-2 -8 0 13
9 -4 -9 4
As you can see, your code has rows of 0's when you subtract a row from itself. The ordering of rows of B are different between the two versions.
Also, half of the rows are just the negation of the other half. Do you need both halves?
ST
ST 2020-12-9
Yes, I need zero rows too. Thanks for your answer.

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Data Type Conversion 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