I would like to know how I can find out how long a certain event lasts.

Hi!

I would like to know how I can find out how long a certain event lasts.

I have this data, where the first column is the time in seconds and the second column is acceleration data.

data =

0.019 0

0.04 0.45371

0.057 0

0.076 0.15127

0.092 0.22037

0.107 0.2317

0.123 0.22781

0.142 0.15654

0.156 0.08676

0.173 0.14319

0.19 0

0.206 0.19837

0.223 0.1897

0.239 0.13603

0.259 0.17579

I would like to know how long the acceleration stayed above a certain threshold (for example: 0.20) and save that value in a new vector each time it exceeds the threshold.

I'm new to using matlab and I'm a bit confused.

thank you very much

Answer 1

[Jan]

data = [ ...
    0.019  0
    0.04   0.45371
    0.057  0
    0.076  0.15127
    0.092  0.22037
    0.107  0.2317
    0.123  0.22781
    0.142  0.15654
    0.156  0.08676
    0.173  0.14319
    0.19   0
    0.206  0.19837
    0.223  0.1897
    0.239  0.13603
    0.259  0.17579];

m   = [false, (data(:, 2) > 0.20).', false];
ini = strfind(m, [false, true]);
fin = strfind(m, [true, false]);  % Or maybe: strfind(m, [true, false]) - 1

iniTime = data(ini, 1)

iniTime = 2×1

0.0400 0.0920

finTime = data(fin, 1)

finTime = 2×1

0.0570 0.1420

spanTime = finTime - iniTime

spanTime = 2×1

0.0170 0.0500

[Liz Román Aguayo]

thank you! it works perfectly!

Answer 2

[Image Analyst]

Do you mean like this:

data = [...
    0.019  0
    0.04  0.45371
    0.057  0
    0.076  0.15127
    0.092  0.22037
    0.107  0.2317
    0.123  0.22781
    0.142  0.15654
    0.156  0.08676
    0.173  0.14319
    0.19  0
    0.206  0.19837
    0.223  0.1897
    0.239  0.13603
    0.259  0.17579];
times = data(:, 1);
values = data(:, 2);
threshold = 0.2;
mask = values > threshold;
% Find distinct regions
[groups, numRegions] = bwlabel(mask)

groups = 15×1

0 1 0 0 2 2 2 0 0 0

numRegions = 2

for k = 1 : numRegions
    thisRegion = groups == k;
    index1 = find(thisRegion, 1, 'first');
    index2 = find(thisRegion, 1, 'last');
    durations(k) = times(index2) - times(index1);
end
durations

durations = 1×2

0 0.0310