remove outlier in large data
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my question how to find outlier in matlab explain by code and example ? and how many methods ? how to find outlier?
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Image Analyst
2014-1-11
Try this:
% data = the variable name of your array
stdDev = std(data(:)) % Compute standard deviation
meanValue = mean(data(:)) % Compute mean
zFactor = 1.5; % or whatever you want.
% Create a binary map of where outliers live.
outliers = abs(data-meanValue) > (zFactor * stdDev);
4 个评论
azar mzory
2014-1-11
Image Analyst
2014-1-11
Try this:
data = 100 + randi(8,10,10)
% Make two outliers
data(2,2) = 5;
data(1,4) = 150
stdDev = std(data(:)) % Compute standard deviation
meanValue = mean(data(:)) % Compute mean
zFactor = 1.5; % or whatever you want.
% Create a binary map of where outliers live.
outliers = abs(data-meanValue) > (zFactor * stdDev)
Be aware that z (how many std devs away from the mean you are) is not that great at finding outliers because if the outlier is huge, it will affect your mean and standard deviation. Just try the above code with data(1,4) = 9999999 to see what I mean. A better measure is the median absolute deviation: http://en.wikipedia.org/wiki/Median_absolute_deviation Or you can try deleteoutliers by Brett http://www.mathworks.com/matlabcentral/fileexchange/3961-deleteoutliers
azar mzory
2014-1-12
Image Analyst
2014-1-15
I don't know how to define outliers in text (words). For example, in this comment that you're reading now, which of the words are "outliers" and why?
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