Find data between min and max

Question

Ahmed Alalawi 2020-1-30

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/502855-find-data-between-min-and-max

评论： Star Strider 2020-1-30

采纳的回答： Star Strider

在 MATLAB Online 中打开

Hello there,

I have used the two functions islocalmin and islocalmax to find minimum and maximum points in my data.

TFmin = islocalmin(task, 'MinProminence',10) 
TFmax = islocalmax(task, 'MinProminence',10)
plot(time_s,task, time_s (TFmin),task(TFmin),'r*')
hold on
plot(time_s,task,time_s(TFmax),task(TFmax),'b*')

I have identified different points as you can see in the attached plots, and I ended up with 10 points.

Now, I need to create two variables (task + time_s) repressing the data that lies in between each minimum and maximum point.

For example (see attached pic):

I need extract the exact date of time and task between the points:

1 and 2

3 and 4

5 and 6

7 and 8

9 and 10

And also the opposite:

2 and 3

4 and 5

6 and 7

8 and 9

Any advice or help would be much appreciated.

Thank you

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Star Strider 2020-1-30

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/502855-find-data-between-min-and-max#answer_412932

在 MATLAB Online 中打开

An accumarray call can do that relatively easily:

D = load('test.mat');
task = D.task;
time_s = D.time_s;
TFmin = islocalmin(task, 'MinProminence',10); 
TFmax = islocalmax(task, 'MinProminence',10);
MinIdx = find(TFmin);
MaxIdx = find(TFmax);
Idx = sort([MinIdx; MaxIdx]);
IdxCell = accumarray(Idx(1:numel(Idx)-1), (1:numel(Idx)-1).', [], @(x){Idx(x):Idx(x+1)});   % Cell Array Of Index Ranges
IdxRng = find(cellfun(@(x)~isempty(x), IdxCell));                                           % Index Ranges
GetData = @(x) [time_s(IdxCell{IdxRng(x)}),  task(IdxCell{IdxRng(x)})];                     % Function To Retrieve Data Easily
Get1 = GetData(1);                                                                          % Get First Set
X1 = Get1(:,1);
Y1 = Get1(:,2);
Get3 = GetData(3);                                                                          % Get Third Set
X3 = Get3(:,1);
Y3 = Get3(:,2);
figure
plot(time_s,task, time_s (TFmin),task(TFmin),'r*')
hold on
plot(time_s,task,time_s(TFmax),task(TFmax),'b*')
plot(X1, Y1, '.r')                                                                          % Plot First Set
plot(X3, Y3, '.g')                                                                          % Plot Third Set
hold off

Producing this example plot:

Find data between min and max - 2020 01 30.png

Thius code recovers all of the intervals, not only the ascending ones, so choose the odd-numbered arguments to ‘GetData’.

2 个评论
显示无隐藏无

Ahmed Alalawi 2020-1-30

Amazing !

Star Strider 2020-1-30

Thank you!

请先登录，再进行评论。

Answer 2

Jeremy 2020-1-30

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/502855-find-data-between-min-and-max#answer_412925

在 MATLAB Online 中打开

Something like this?

t = linspace(0,2*pi,201);
y = sin(t);
plot(t,y,'LineWidth',2)
grid on
hold on
minid = find(islocalmin(y));
maxid = find(islocalmax(y));
[~,d] = min([minid maxid])
switch d
    case 1
        data_id = minid:1:maxid;
    case 2
        data_id = maxid:1:minid;
end
t_int = t(data_id);
y_int = y(data_id);
plot(t_int,y_int,'r--','LineWidth',2)