# Identify when a exceedance occurs and return the start point and length of each exceedance

2 vues (au cours des 30 derniers jours)
Tyler le 20 Juin 2024
Réponse apportée : Voss le 20 Juin 2024
I have two large arrays with magnetic heading values:
hdg1=[10;10;10;10;10;10;10;10;10;10;10;10]; %actual data is thousands of values.
hdg2=[12;18;18;18;13;14;10;20;20;12;13;12];
calculate delta between each item.
hdgdelta = abs(hdg1 - hdg2);
Need help with:
Identifying when and how long hdgdelta values are greater than say 6.
I would like to see the results returned as such:
Array1: The starting points/rows where hdgdelta exceedance groups exceed the value of 6. (Rows 2 and 8 in this case).
Array2: The duration of those splits. i.e The duration/count for when subsequent rows have a value greater than 6. Ie. 2,3,4, (length of 3) and 8,9 (length of 2)
The example result that I would like to see:
Array1 = [2;8]; %starting points/rows where exceedance happen
Array2 = [3;2]; %duration (in # of rows) for each exceedance.
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### Réponses (1)

Voss le 20 Juin 2024
One way is to use strfind to find the starts and ends of the sections where hdgdelta>=6:
hdg1=[10;10;10;10;10;10;10;10;10;10;10;10]; %actual data is thousands of values.
hdg2=[12;18;18;18;13;14;10;20;20;12;13;12];
hdgdelta = abs(hdg1 - hdg2);
idx = hdgdelta(:).' >= 6
idx = 1x12 logical array
0 1 1 1 0 0 0 1 1 0 0 0
start_idx = strfind([false,idx],[false,true])
start_idx = 1x2
2 8
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end_idx = strfind([idx,false],[true,false])
end_idx = 1x2
4 9
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Array1 = start_idx(:);
Array2 = end_idx(:)-start_idx(:)+1;
disp(Array1)
2 8
disp(Array2)
3 2
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