MATLAB: Normalize data without influence from outliers

voltage normalization

I have some time vs. voltage data that I would like to normalize, but there are some voltage outliers. The outlier peaks are meaningful and I do not want to remove them. Is there any way to normalize the data without influence from the outliers in the calculation? I want the "steady state" in my data to be around 0, and I still want to determine the Z score of those voltage peaks based on the normalization of data around the steady state.

The way I'm doing it now is gathering another set of data without the peaks, finding the mean and SD, and then manually using that to normalize the data with the peaks. It works but it is not very elegant. Is there a better way?

Best Answer

Molly,

I think the devil is in the details here, and you haven't shown us any code. The approach will depend on whether this is a one-off solution. Do you need this code to determine the outlier cutoff automatically, or you can just hard-code it this one time?

So, for example, if your voltage data are in a variable called voltageData, then you could identify the outliers with an boolean index

outlierIndex = (voltageData>137); % Hard-coded voltage outlier definition

and then use that index to exclude some data from other calculations:

meanVoltageWithoutOutlier = mean(voltageData(not(outlierIndex)));

etc.

It's difficult to give you much more advice without details from you.

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Srinidhi - how many of these voltages to you expect to acquire? if you need to store the value in an array, then you can do so by just creating the array ahead of time (outside your for or while loop) and then update that array with the voltage data. Consider the following

 % create an array of 10000 elements to store the voltage data
 voltageData = zeros(10000,1);
 % track the current voltage index
 voltageIdx  = 0;
 % communicate with Arduino
 while true
     % get the voltage data
     voltValue = ...;
     % save it to the array
     voltageIdx  = voltageIdx + 1;
     voltageData(voltageIdx) = voltValue;
 end

Without knowing exactly how your code is written, you can try the above which will allow you to collect the voltage data over time.

Best Answer

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