Mathematics

Removing Outliers

You can remove outliers or misplaced data points from a data set in much the same manner as NaNs. For the vehicle traffic count data, the mean and standard deviations of each column of the data are

• mu = mean(count)
  sigma = std(count)
  
  mu =
         32.0000   46.5417   65.5833
  
  sigma =
         25.3703   41.4057   68.0281
  

The number of rows with outliers greater than three standard deviations is obtained with

• [n,p] = size(count)
  outliers = abs(count - mu(ones(n, 1),:)) > 3*sigma(ones(n, 1),:);
  nout = sum(outliers)
  nout =
         1    0    0
  

There is one outlier in the first column. Remove this entire observation with

• count(any(outliers'),:) = [];
  

Data Preprocessing

Regression and Curve Fitting