Getting Started

Multivariate Data

MATLAB uses column-oriented analysis for multivariate statistical data. Each column in a data set represents a variable and each row an observation. The (i,j)th element is the ith observation of the jth variable.

As an example, consider a data set with three variables:

• Heart rate
• Weight
• Hours of exercise per week

For five observations, the resulting array might look like

• D =
         72          134          3.2
         81          201          3.5
         69          156          7.1
         82          148          2.4
         75          170          1.2
  

The first row contains the heart rate, weight, and exercise hours for patient 1, the second row contains the data for patient 2, and so on. Now you can apply many MATLAB data analysis functions to this data set. For example, to obtain the mean and standard deviation of each column

• mu = mean(D), sigma = std(D)
  
  mu =
        75.8       161.8         3.48
  
  sigma =
      5.6303      25.499       2.2107
  

For a list of the data analysis functions available in MATLAB, type

• help datafun
  

If you have access to the Statistics Toolbox, type

• help stats
  

Arrays

Scalar Expansion