Finding the max value out of 1000 sample set at every second.

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Kawalpreet Kaur 2021-10-26

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回答： Pranjal Kaura 2021-10-29

Hi,

I have a data set collected time versus strain. Strain data is collected at multiple points. So, I have one column for the X-axis and multiple columns for the Y-axis.

The sample data is collected 1000 times every second. I want to get the maximum value for strain at every second (out of 1000 samples) and plot it against the time. The test runs for 4 hours, so I want to convert the time from seconds to hours.

So, there will be multiple lines for the Y-axis in the plot.

I am looking forward to any help.

Thanks

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VBBV 2021-10-27

在 MATLAB Online 中打开

for i = 1:10

xy(:,i) = unidrnd(1000,1000*60*60,1); % strain data

end

T =1:length(xy)/1000; % time data

[V I] = max(xy(1:1000:end,:))

V = 1×10

1000 1000 1000 1000 1000 1000 1000 999 1000 1000

I = 1×10

768 54 56 2044 226 133 5 3339 1871 870

plot(T(I),V)

Try this

Kawalpreet Kaur 2021-10-27

Thank you for your reply. I appreciate it.

Let me put my question in this way.

I have a data set collected time (VarName2) versus strain (VarName3, VarName4, VarName5, VarName6..... and so on until col U). So, I have one column for the X-axis and multiple columns for the Y-axis.

The sample data is collected 1000 times every second. I want to get the maximum value for strain at every second (out of 1000 samples) and want to plot the graph time on X axis (convert from seconds to hours) and on Y axis (all the strain values representing in different columns). I have million of rows for this data set.

I am looking forward to any help. Thank you.

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Answer 1

Pranjal Kaura 2021-10-29

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在 MATLAB Online 中打开

Hey Kawalpreet,

You can refer to the following code snippet wherein I've tried to replicate your usecase and provided a solution.

sample_rate = 10; %1000 for you
num_rows = 1000; %1 million for you
pd = makedist('Normal');
VarName3 = random(pd, [num_rows, 1]);
VarName4 = random(pd, [num_rows, 1]);
dataset = [VarName3 VarName4];
dataset_sampled = reshape(dataset, sample_rate, num_rows/sample_rate, size(dataset, 2));
dataset_sampled_max = squeeze(max(dataset_sampled, [], 1));
time_sec = 1:length(dataset_sampled_max);
time_hours = time_sec/3600;
plot(time_hours, dataset_sampled_max);
xlabel("Time in Hours");

You can refer to the 'plot' documentation to know more about addings labels, legends, color etc to the plot.

Hope this helps!

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