Applied Statistics Using SPSS, STATISTICA, MATLAB and R

3.2 Estimating a Mean 91
Figure 3.5. Selection of cases: a) Partial view of STATISTICA “Case Selection
Conditions” window; b) Partial view of SPSS “Select Cases” window.
In MATLAB one may select a submatrix of matrix x based on a particular
value, a, of a column i using the construction x(x(:,i)==a,:). For instance,
assuming the first column of cork contains the classifications of the cork
stoppers, c = cork(cork(:,1)==1,:) will retrieve the submatrix of cork
corresponding to the first 50 cases of class 1. Other relational operators can be used
instead of the equality operator “== ” . (Attention: “= ” is an assignment operator,
an equality operator.) For instance, c = cork(cork(:,1)> filter = round(unifrnd(0,1,150,1));
>> fcork = cork(filter==1,:);
> filter fcork