matlab - 从矩阵中提取正值和负值

Question

我有这样的 3D 矩阵

1   5648.00278672228    -46.43159546036
1   5650.38906894239    68.81787768047
1   5649.13081105839    -4867.55961979647
1   5650.53055771227    4868.95936645035
1   5647.95215053492    4866.38095927300
1   5650.21656586142    -2328.64537459950
1   5651.76371933598    7870.19252807406
1   5649.87288540620    -1168.30169414428

我想将第 3 列的正值和负值提取到两个单独的二维矩阵(POS 和 NEG)中，其中第 1 列包含上述矩阵中行的索引，第二列包含值。

结果应该是这样的

POS = 
2   68.81787768047
4   4868.95936645035
5   4866.38095927300
7   7870.19252807406

和

NEG =  
1   -46.43159546036
3   -4867.55961979647
6   -2328.64537459950
8   -1168.30169414428

Answer 1

您可以使用find 函数和逻辑索引

POS = [find(A(:,3)>0) A(A(:,3)>0,3)]
NEG = [find(A(:,3)<=0) A(A(:,3)<=0,3)]

对于你的输入矩阵是 A

A = [1   5648.00278672228    -46.43159546036
    1   5650.38906894239    68.81787768047
    1   5649.13081105839    -4867.55961979647
    1   5650.53055771227    4868.95936645035
    1   5647.95215053492    4866.38095927300
    1   5650.21656586142    -2328.64537459950
    1   5651.76371933598    7870.19252807406
    1   5649.87288540620    -1168.30169414428]

结果将是(使用format shortG)

POS =

        2       68.818
        4         4869
        5       4866.4
        7       7870.2


NEG =

        1      -46.432
        3      -4867.6
        6      -2328.6
        8      -1168.3

由于@Dennis Jaheruddin 和 Khurram Majeed 的评论，第二个发现已被删除。