如何根据列中的值在matlab中将行与矩阵分开？

Question

我有一个矩阵，它是从文本文件中读取的二维数组。每行文本文件有3个条目。第3列的值范围为1到4.我想基于此值分隔行并将它们放入不同的矩阵中。你能建议一个办法吗？

Answer 1

对于矩阵M，正如您所描述的那样

rowsContainingOne   = M( M(:,3)==1, :)
rowsContainingTwo   = M( M(:,3)==2, :)
rowsContainingThree = M( M(:,3)==3, :)
rowsContainingFour  = M( M(:,3)==4, :)

要了解其工作原理，请查看以下部分的结果：

M(:,3)              %A vector of column three
M(:,3)==1           %A logical array, `true` where column 3 equals one
M( M(:,3)==1, :)    %All columns (indicated by `:`) from rows where the logical array is `true`

Answer 2

使用函数sortrows。

伪代码：

%% Creating a matrix of the type you have mentioned.
A = zeros(10,3);   A(:,1:2) = rand(10,2);    A(:,3)=randi(4,10,1);
%% Use the "sortrows" function to sort all the rows as per the entries in column-3 of A    
B = sortrows(A,3);