Question

我想选择矩阵的两个随机列并交换它们。我用：

S(:,[round_i round_j]) = S(:,[round_j round_i]);

但是我的代码似乎产生了和以前一样的矩阵。下面是代码片段和命令窗口的输出。

function swapped_schedule=swapRounds(S)
global weeks;

round_i=randi(weeks)
round_j=randi(weeks)

while round_j~=round_i
    round_j=randi(weeks);
end

S(:,[round_i round_j]) = S(:,[round_j round_i]);

swapped_schedule=S;

end

Schedule是我传递给函数swapRounds()的矩阵。输出如下所示：

schedule =

     4    -4    -6     5    -2     6     2     3    -5    -3
     5    -6    -4     4     1     3    -1    -5    -3     6
    -6     5    -5     6     4    -2    -4    -1     2     1
    -1     1     2    -2    -3     5     3    -6     6    -5
    -2    -3     3    -1    -6    -4     6     2     1     4
     3     2     1    -3     5    -1    -5     4    -4    -2


round_i =

     4


round_j =

     6


ans =

     4    -4    -6     5    -2     6     2     3    -5    -3
     5    -6    -4     4     1     3    -1    -5    -3     6
    -6     5    -5     6     4    -2    -4    -1     2     1
    -1     1     2    -2    -3     5     3    -6     6    -5
    -2    -3     3    -1    -6    -4     6     2     1     4
     3     2     1    -3     5    -1    -5     4    -4    -2

如何让这段代码交换我的两列？

Answer 1

schedule = rand(6,10);
round_i = 4;
round_j = 6;

[rows,cols] = size(schedule); % get number of cols
colIDX = 1:cols; % create an index array
colIDX(round_i) = round_j;
colIDX(round_j) = round_i; % flip indices

schedule2 = schedule(:,colIDX); % rename to schedule if wanted

基本上，您应该使用数组索引列，而不仅仅是两个数字。见this highly informative post on indexing in MATLAB

交换两列不工作

1 个答案: