Matlab:在表格中按每组获得排名前/后2位的观测结果

Question

我想在matlab的一个表中获得每组排名前两位和后两位的观测结果。我没有可用的组过滤器功能。

我有一张这样的桌子：

MeasurementTime = datetime({'2015-12-18 08:03:05';'2015-12-18 10:03:17';'2015-12-18 12:03:13'});
VAR1 = [37.3;39.1;42.3];
VAR2 = [30.1;30.03;29.9];
VAR3 = [13.4;6.5;7.3];
VAR4 = [3.4;1.5;0.3];
VAR5 = [3.9;1.1;0.2];
TT = timetable(MeasurementTime,VAR1, VAR2, VAR3, VAR4, VAR5)
TT1 = stack(TT, {'VAR1','VAR2','VAR3','VAR4','VAR5'},'NewDataVariableName','Value','IndexVariableName','Group')

MeasurementTime       Group    Value
____________________    _____    _____
18-Dec-2015 08:03:05    VAR1      37.3
18-Dec-2015 08:03:05    VAR2      30.1
18-Dec-2015 08:03:05    VAR3      13.4
18-Dec-2015 08:03:05    VAR4       3.4
18-Dec-2015 08:03:05    VAR5       3.9
18-Dec-2015 10:03:17    VAR1      39.1
18-Dec-2015 10:03:17    VAR2     30.03
18-Dec-2015 10:03:17    VAR3       6.5
18-Dec-2015 10:03:17    VAR4       1.5
18-Dec-2015 10:03:17    VAR5       1.1
18-Dec-2015 12:03:13    VAR1      42.3
18-Dec-2015 12:03:13    VAR2      29.9
18-Dec-2015 12:03:13    VAR3       7.3
18-Dec-2015 12:03:13    VAR4       0.3
18-Dec-2015 12:03:13    VAR5       0.2

该组是MeasurementTime。理想情况下，我希望这是前2个观察结果：

MeasurementTime       Group    Value
____________________    _____    _____
18-Dec-2015 08:03:05    VAR1      37.3
18-Dec-2015 08:03:05    VAR2      30.1
18-Dec-2015 10:03:17    VAR1      39.1
18-Dec-2015 10:03:17    VAR2     30.03
18-Dec-2015 12:03:13    VAR1      42.3
18-Dec-2015 12:03:13    VAR2      29.9

对于底部2个观测值：

MeasurementTime       Group    Value
____________________    _____    _____
18-Dec-2015 08:03:05    VAR4       3.4
18-Dec-2015 08:03:05    VAR5       3.9
18-Dec-2015 10:03:17    VAR4       1.5
18-Dec-2015 10:03:17    VAR5       1.1
18-Dec-2015 12:03:13    VAR4       0.3
18-Dec-2015 12:03:13    VAR5       0.2

有什么想法吗？

Answer 1

我不确定你说的"前2个观察结果"；以及"；底部2个观察值"；，不幸的是，我不能发表评论，所以我将尝试将您想要的输出复制为：

TTtop2 = stack(TT(:,1:2),{'VAR1','VAR2'},'NewDataVariableName','Value','IndexVariableName','Group')
TTbottom2 = stack(TT(:,4:5),{'VAR4','VAR5'},'NewDataVariableName','Value','IndexVariableName','Group')